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BGP UPDATE-SOURCE LOOPBACK PROBLEM

williammanurung
Level 1
Level 1

‎05-23-2017 08:37 PM - edited ‎03-05-2019 08:35 AM

Hello guys,


As my topology, i have configuration like this:


Router 1:

interface Loopback0
   ip address 7.7.7.7 255.255.255.255

interface FastEthernet2/0
 ip address 1.1.1.1 255.255.255.252

router bgp 100
 no synchronization
 bgp router-id 7.7.7.7
 bgp log-neighbor-changes
 network 100.100.100.100 mask 255.255.255.255
 neighbor 8.8.8.8 remote-as 200
 neighbor 8.8.8.8 ebgp-multihop 255
 neighbor 8.8.8.8 update-source Loopback0
 neighbor 8.8.8.8 soft-reconfiguration inbound
 no auto-summary

ip route 8.8.8.8 255.255.255.255 1.1.1.2


Router 2:

interface Loopback0
 ip address 8.8.8.8 255.255.255.255

interface FastEthernet2/0
 ip address 1.1.1.2 255.255.255.252
router bgp 200
 no synchronization
 bgp router-id 8.8.8.8
 bgp log-neighbor-changes
 network 200.200.200.200 mask 255.255.255.255
 neighbor 7.7.7.7 remote-as 100
 neighbor 7.7.7.7 ebgp-multihop 255
 neighbor 7.7.7.7 soft-reconfiguration inbound
 no auto-summary

router bgp 200
 no synchronization
 bgp router-id 8.8.8.8
 bgp log-neighbor-changes
 network 200.200.200.200 mask 255.255.255.255
 neighbor 7.7.7.7 remote-as 100
 neighbor 7.7.7.7 ebgp-multihop 255
 neighbor 7.7.7.7 soft-reconfiguration inbound
 no auto-summary


ip route 7.7.7.7 255.255.255.255 1.1.1.1​

What i want to ask is how can the router 2 adjacency with router 1 without router 2 configure neighbor 7.7.7.7​ update-source loopback0 ?

Topologi

LOG Router1:

R1#debug ip packet detail
IP packet debugging is on (detailed)
R1#
*May 24 09:54:19.783: %BGP-5-ADJCHANGE: neighbor 8.8.8.8 Down User reset
*May 24 09:54:19.783: %BGP_SESSION-5-ADJCHANGE: neighbor 8.8.8.8 IPv4 Unicast topo                                                                                      logy base removed from session  User reset
*May 24 09:54:20.083: %BGP-5-ADJCHANGE: neighbor 8.8.8.8 Up
*May 24 09:54:21.011: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:21.011: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:21.015: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:21.015: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:21.015: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:21.019: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:21.255: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, input fe                                                                                      ature
*May 24 09:54:21.255:     TCP src=179, dst=22333, seq=1782251625, ack=1978533418,                                                                                       win=16265 ACK, MCI Check(62), rtype
R1#0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:21.255: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8.8.8 dst 7.7.7.7
*May 24 09:54:21.255: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:21.255: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:21.255: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, rcvd 2
*May 24 09:54:21.255:     TCP src=179, dst=22333, seq=1782251625, ack=1978533418,                                                                                       win=16265 ACK
*May 24 09:54:21.259: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:21.259:     TCP src=179, dst=22333, seq=1782251625, ack=1978533418,                                                                                       win=16265 ACK
*May 24 09:54:21.931: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, input fe                                                                                      ature
*May 24 09:54:21.931:     TCP src=179, dst=22333, seq=1782251625, ack=1978533418,                                                                                       win=16265 ACK PSH FIN, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:21.931: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8
R1#.8.8 dst 7.7.7.7
*May 24 09:54:21.931: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:21.931: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:21.931: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, rcvd 2
*May 24 09:54:21.931:     TCP src=179, dst=22333, seq=1782251625, ack=1978533418,                                                                                       win=16265 ACK PSH FIN
*May 24 09:54:21.931: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:21.931:     TCP src=179, dst=22333, seq=1782251625, ack=1978533418,                                                                                       win=16265 ACK PSH FIN
*May 24 09:54:21.931: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:21.931: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:21.931: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:21.931: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:21.931: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:21.9
R1#31: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0), routed via F                                                                                      IB
*May 24 09:54:21.935: %BGP-5-ADJCHANGE: neighbor 8.8.8.8 Down Peer closed the sess                                                                                      ion
*May 24 09:54:21.935: %BGP_SESSION-5-ADJCHANGE: neighbor 8.8.8.8 IPv4 Unicast topo                                                                                      logy base removed from session  Peer closed the session
*May 24 09:54:21.955: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, input fe                                                                                      ature
*May 24 09:54:21.955:     TCP src=179, dst=22333, seq=1782251626, ack=1978533419,                                                                                       win=16265 ACK, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:21.959: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8.8.8 dst 7.7.7.7
*May 24 09:54:21.959: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:21.959: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:21.959: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, rcvd 2
*May 24 09:54:21.959:     TCP src=179, dst=22333, seq=1782251626, ack=1978533419,                                                                                       win=16265 ACK
*May 24 09:54:21.959: IP: s=
R1#8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, stop process pak for forus packet
*May 24 09:54:21.959:     TCP src=179, dst=22333, seq=1782251626, ack=1978533419,                                                                                       win=16265 ACK
*May 24 09:54:22.107: IP: s=1.1.1.2 (FastEthernet2/0), d=7.7.7.7, len 44, input fe                                                                                      ature
*May 24 09:54:22.107:     TCP src=54875, dst=179, seq=583077092, ack=0, win=16384                                                                                       SYN, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:22.107: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 1                                                                                      .1.1.2 dst 7.7.7.7
*May 24 09:54:22.107: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:22.107: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:22.107: IP: s=1.1.1.2 (FastEthernet2/0), d=7.7.7.7, len 44, rcvd 2
*May 24 09:54:22.107:     TCP src=54875, dst=179, seq=583077092, ack=0, win=16384                                                                                       SYN
*May 24 09:54:22.107: IP: s=1.1.1.2 (FastEthernet2/0), d=7.7.7.7, len 44, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:22.107:     TCP src=54875, dst=179, seq=583077092, ack=0
R1#, win=16384 SYN
*May 24 09:54:22.107: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 1.1.1.2
*May 24 09:54:22.107: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:22.107: IP: tableid=0, s=7.7.7.7 (local), d=1.1.1.2 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:22.107: IP: s=7.7.7.7 (local), d=1.1.1.2 (FastEthernet2/0), len 40,                                                                                       sending
*May 24 09:54:22.107:     TCP src=179, dst=54875, seq=0, ack=583077093, win=0 ACK                                                                                       RST
*May 24 09:54:22.107: IP: s=7.7.7.7 (local), d=1.1.1.2 (FastEthernet2/0), len 40,                                                                                       sending full packet
*May 24 09:54:22.107:     TCP src=179, dst=54875, seq=0, ack=583077093, win=0 ACK                                                                                       RST
R1#
*May 24 09:54:30.211: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:30.211: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.211: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.235: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 44, input fe                                                                                      ature
*May 24 09:54:30.235:     TCP src=179, dst=44679, seq=3805719326, ack=1718523688,                                                                                       win=16384 ACK SYN, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.239: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8.8.8 dst 7.7.7.7
*May 24 09:54:30.239: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:30.239: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.239: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 44, rcvd 2
*May 24 09:54:30.239:     TCP src=179, dst=44679, seq=3805719326, ack=1718523688,                                                                                       win=16384 ACK SYN
*May 24 09:54:30.239: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.
R1#7, len 44, stop process pak for forus packet
*May 24 09:54:30.239:     TCP src=179, dst=44679, seq=3805719326, ack=1718523688,                                                                                       win=16384 ACK SYN
*May 24 09:54:30.239: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:30.239: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.239: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.239: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:30.239: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.239: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.255: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 98, input fe                                                                                      ature
*May 24 09:54:30.255:     TCP src=179, dst=44679, seq=3805719327, ack=1718523746,                                                                                       win=16326 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.259: FIBipv4-packet-proc: route packet from FastEthernet2
R1#/0 src 8.8.8.8 dst 7.7.7.7
*May 24 09:54:30.259: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:30.259: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.259: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 98, rcvd 2
*May 24 09:54:30.259:     TCP src=179, dst=44679, seq=3805719327, ack=1718523746,                                                                                       win=16326 ACK PSH
*May 24 09:54:30.259: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 98, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.259:     TCP src=179, dst=44679, seq=3805719327, ack=1718523746,                                                                                       win=16326 ACK PSH
*May 24 09:54:30.259: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 59, input fe                                                                                      ature
*May 24 09:54:30.259:     TCP src=179, dst=44679, seq=3805719385, ack=1718523746,                                                                                       win=16326 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.259: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8.8.8 dst 7.7.7.7
*May 24 09:54:30.259: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:30.259:
R1#FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.259: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 59, rcvd 2
*May 24 09:54:30.259:     TCP src=179, dst=44679, seq=3805719385, ack=1718523746,                                                                                       win=16326 ACK PSH
*May 24 09:54:30.263: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 59, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.263:     TCP src=179, dst=44679, seq=3805719385, ack=1718523746,                                                                                       win=16326 ACK PSH
*May 24 09:54:30.263: %BGP-5-ADJCHANGE: neighbor 8.8.8.8 Up
*May 24 09:54:30.263: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:30.263: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.263: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.267: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:30.267: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.267: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEt
R1#hernet2/0), routed via FIB
*May 24 09:54:30.267: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:30.267: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.267: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.287: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 59, input fe                                                                                      ature
*May 24 09:54:30.291:     TCP src=179, dst=44679, seq=3805719404, ack=1718523807,                                                                                       win=16265 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.291: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8.8.8 dst 7.7.7.7
*May 24 09:54:30.291: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:30.291: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.291: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 59, rcvd 2
*May 24 09:54:30.291:     TCP src=179, dst=44679, seq=3805719404, ack=1718523807,                                                                                       win=16265 ACK PSH
*May 24 09:54:30.291: IP: s=8.8.8.8 (
R1#FastEthernet2/0), d=7.7.7.7, len 59, stop process pak for forus packet
*May 24 09:54:30.291:     TCP src=179, dst=44679, seq=3805719404, ack=1718523807,                                                                                       win=16265 ACK PSH
*May 24 09:54:30.291: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 63, input fe                                                                                      ature
*May 24 09:54:30.291:     TCP src=179, dst=44679, seq=3805719423, ack=1718523807,                                                                                       win=16265 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.291: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8.8.8 dst 7.7.7.7
*May 24 09:54:30.291: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:30.291: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.291: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 63, rcvd 2
*May 24 09:54:30.291:     TCP src=179, dst=44679, seq=3805719423, ack=1718523807,                                                                                       win=16265 ACK PSH
*May 24 09:54:30.291: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 63, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.295:     TCP src=179, dst=4467
R1#9, seq=3805719423, ack=1718523807, win=16265 ACK PSH
*May 24 09:54:30.491: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:30.495: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.495: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
R1#
*May 24 09:54:54.423: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 95, input fe                                                                                      ature
*May 24 09:54:54.423:     TCP src=179, dst=44679, seq=3805719446, ack=1718523807,                                                                                       win=16265 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:54.423: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8.8.8 dst 7.7.7.7
*May 24 09:54:54.423: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:54.423: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:54.423: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 95, rcvd 2
*May 24 09:54:54.423:     TCP src=179, dst=44679, seq=3805719446, ack=1718523807,                                                                                       win=16265 ACK PSH
R1#
*May 24 09:54:54.423: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 95, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:54.423:     TCP src=179, dst=44679, seq=3805719446, ack=1718523807,                                                                                       win=16265 ACK PSH
*May 24 09:54:54.539: FIBipv4-packet-proc: route packet from (local) src 7.7.7.7 d                                                                                      st 8.8.8.8
*May 24 09:54:54.539: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:54.539: IP: tableid=0, s=7.7.7.7 (local), d=8.8.8.8 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:54.835: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, input fe                                                                                      ature
*May 24 09:54:54.835:     TCP src=179, dst=44679, seq=3805719501, ack=1718523862,                                                                                       win=16210 ACK
R1#, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:54.839: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 8                                                                                      .8.8.8 dst 7.7.7.7
*May 24 09:54:54.839: FIBfwd-proc: Default:7.7.7.7/32 recieve entry
*May 24 09:54:54.843: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:54.843: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, rcvd 2
*May 24 09:54:54.843:     TCP src=179, dst=44679, seq=3805719501, ack=1718523862,                                                                                       win=16210 ACK
*May 24 09:54:54.847: IP: s=8.8.8.8 (FastEthernet2/0), d=7.7.7.7, len 40, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:54.847:     TCP src=179, dst=44679, seq=3805719501, ack=1718523862,                                                                                       win=16210 ACK

LOG Router2:

R2#
*May 24 09:54:19.683: %BGP-5-ADJCHANGE: neighbor 7.7.7.7 Down Peer closed the sess                                                                                      ion
*May 24 09:54:19.683: %BGP_SESSION-5-ADJCHANGE: neighbor 7.7.7.7 IPv4 Unicast topo                                                                                      logy base removed from session  Peer closed the session
*May 24 09:54:19.987: %BGP-5-ADJCHANGE: neighbor 7.7.7.7 Up
R2#term leng 0
R2#
R2#clear ip bgp *
R2#
R2#debug ip packet detail
IP packet debugging is on (detailed)
R2#
*May 24 09:54:21.807: %BGP-5-ADJCHANGE: neighbor 7.7.7.7 Down User reset
*May 24 09:54:21.807: %BGP_SESSION-5-ADJCHANGE: neighbor 7.7.7.7 IPv4 Unicast topo                                                                                      logy base removed from session  User reset
R2#
*May 24 09:54:30.107: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 44, input fe                                                                                      ature
*May 24 09:54:30.107:     TCP src=44679, dst=179, seq=1718523687, ack=0, win=16384                                                                                       SYN, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.111: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 7                                                                                      .7.7.7 dst 8.8.8.8
*May 24 09:54:30.111: FIBfwd-proc: Default:8.8.8.8/32 recieve entry
*May 24 09:54:30.111: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.115: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 44, rcvd 2
*May 24 09:54:30.115:     TCP src=44679, dst=179, seq=1718523687, ack=0, win=16384                                                                                       SYN
*May 24 09:54:30.115: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 44, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.115:     TCP src=44679, dst=179, seq=1718523687, ack=0, win=16384                                                                                       SYN
*May 24 09:54:30.115: FIBipv4-packet-proc: route packet from (local) src 8.8.8.8 d                                                                                      st 7.7.7.7
*May 24 09:54:30.115: FIBipv4-packet-proc: packet routing succ
R2#eeded
*May 24 09:54:30.115: IP: tableid=0, s=8.8.8.8 (local), d=7.7.7.7 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.127: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 40, input fe                                                                                      ature
*May 24 09:54:30.131:     TCP src=44679, dst=179, seq=1718523688, ack=3805719327,                                                                                       win=16384 ACK, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.131: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 7                                                                                      .7.7.7 dst 8.8.8.8
*May 24 09:54:30.131: FIBfwd-proc: Default:8.8.8.8/32 recieve entry
*May 24 09:54:30.131: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.131: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 40, rcvd 2
*May 24 09:54:30.131:     TCP src=44679, dst=179, seq=1718523688, ack=3805719327,                                                                                       win=16384 ACK
*May 24 09:54:30.131: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 40, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.131:     TCP src=44679, dst=179, seq=1718523688, ack=3805719327,                                                                                       win=16384 ACK
*May 24 09:54:30.131: I
R2#P: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 98, input feature
*May 24 09:54:30.131:     TCP src=44679, dst=179, seq=1718523688, ack=3805719327,                                                                                       win=16384 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.131: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 7                                                                                      .7.7.7 dst 8.8.8.8
*May 24 09:54:30.131: FIBfwd-proc: Default:8.8.8.8/32 recieve entry
*May 24 09:54:30.131: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.131: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 98, rcvd 2
*May 24 09:54:30.135:     TCP src=44679, dst=179, seq=1718523688, ack=3805719327,                                                                                       win=16384 ACK PSH
*May 24 09:54:30.135: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 98, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.135:     TCP src=44679, dst=179, seq=1718523688, ack=3805719327,                                                                                       win=16384 ACK PSH
*May 24 09:54:30.135: FIBipv4-packet-proc: route packet from (local) src 8.8.8.8 d                                                                                      st 7.7.7.7
*May 24 09:54:30.135: FIBipv4-packet-proc: packe
R2#t routing succeeded
*May 24 09:54:30.135: IP: tableid=0, s=8.8.8.8 (local), d=7.7.7.7 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.135: FIBipv4-packet-proc: route packet from (local) src 8.8.8.8 d                                                                                      st 7.7.7.7
*May 24 09:54:30.135: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.135: IP: tableid=0, s=8.8.8.8 (local), d=7.7.7.7 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 59, input fe                                                                                      ature
*May 24 09:54:30.151:     TCP src=44679, dst=179, seq=1718523746, ack=3805719404,                                                                                       win=16307 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.151: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 7                                                                                      .7.7.7 dst 8.8.8.8
*May 24 09:54:30.151: FIBfwd-proc: Default:8.8.8.8/32 recieve entry
*May 24 09:54:30.151: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 59, rcvd 2
*May 24 09:54:30.151:     TCP src=44679, dst
R2#=179, seq=1718523746, ack=3805719404, win=16307 ACK PSH
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 59, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.151:     TCP src=44679, dst=179, seq=1718523746, ack=3805719404,                                                                                       win=16307 ACK PSH
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 59, input fe                                                                                      ature
*May 24 09:54:30.151:     TCP src=44679, dst=179, seq=1718523765, ack=3805719404,                                                                                       win=16307 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.151: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 7                                                                                      .7.7.7 dst 8.8.8.8
*May 24 09:54:30.151: FIBfwd-proc: Default:8.8.8.8/32 recieve entry
*May 24 09:54:30.151: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 59, rcvd 2
*May 24 09:54:30.151:     TCP src=44679, dst=179, seq=1718523765, ack=3805719404,                                                                                       win=16307 ACK PSH
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8
R2#.8, len 59, stop process pak for forus packet
*May 24 09:54:30.151:     TCP src=44679, dst=179, seq=1718523765, ack=3805719404,                                                                                       win=16307 ACK PSH
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 63, input fe                                                                                      ature
*May 24 09:54:30.151:     TCP src=44679, dst=179, seq=1718523784, ack=3805719404,                                                                                       win=16307 ACK PSH, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.151: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 7                                                                                      .7.7.7 dst 8.8.8.8
*May 24 09:54:30.151: FIBfwd-proc: Default:8.8.8.8/32 recieve entry
*May 24 09:54:30.151: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 63, rcvd 2
*May 24 09:54:30.151:     TCP src=44679, dst=179, seq=1718523784, ack=3805719404,                                                                                       win=16307 ACK PSH
*May 24 09:54:30.151: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 63, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.151:     TCP src=44679, dst=179, seq=1718523784, ack=38
R2#05719404, win=16307 ACK PSH
*May 24 09:54:30.151: %BGP-5-ADJCHANGE: neighbor 7.7.7.7 Up
*May 24 09:54:30.171: FIBipv4-packet-proc: route packet from (local) src 8.8.8.8 d                                                                                      st 7.7.7.7
*May 24 09:54:30.171: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.171: IP: tableid=0, s=8.8.8.8 (local), d=7.7.7.7 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.171: FIBipv4-packet-proc: route packet from (local) src 8.8.8.8 d                                                                                      st 7.7.7.7
*May 24 09:54:30.171: FIBipv4-packet-proc: packet routing succeeded
*May 24 09:54:30.171: IP: tableid=0, s=8.8.8.8 (local), d=7.7.7.7 (FastEthernet2/0                                                                                      ), routed via FIB
*May 24 09:54:30.383: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 40, input fe                                                                                      ature
*May 24 09:54:30.383:     TCP src=44679, dst=179, seq=1718523807, ack=3805719446,                                                                                       win=16265 ACK, MCI Check(62), rtype 0, forus FALSE, sendself FALSE, mtu 0
*May 24 09:54:30.383: FIBipv4-packet-proc: route packet from FastEthernet2/0 src 7                                                                                      .7.7.7 dst 8.8.8.8
*May 24 09:54:30.383: FIBfwd-pro
R2#c: Default:8.8.8.8/32 recieve entry
*May 24 09:54:30.383: FIBipv4-packet-proc: packet routing failed
*May 24 09:54:30.383: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 40, rcvd 2
*May 24 09:54:30.383:     TCP src=44679, dst=179, seq=1718523807, ack=3805719446,                                                                                       win=16265 ACK
*May 24 09:54:30.383: IP: s=7.7.7.7 (FastEthernet2/0), d=8.8.8.8, len 40, stop pro                                                                                      cess pak for forus packet
*May 24 09:54:30.383:     TCP src=44679, dst=179, seq=1718523807, ack=3805719446,                                                                                       win=16265 ACK
R2#sh ip bgp nei
R2#sh ip bgp neighbors
BGP neighbor is 7.7.7.7,  remote AS 100, external link
  BGP version 4, remote router ID 7.7.7.7
  BGP state = Established, up for 00:00:20
  Last read 00:00:20, last write 00:00:20, hold time is 180, keepalive interval is                                                                                       60 seconds
  Neighbor sessions:
    1 active, is multisession capable
  Neighbor capabilities:
    Route refresh: advertised and received(new)
    Four-octets ASN Capability: advertised and received
    Address family IPv4 Unicast: advertised and received
    Multisession Capability: advertised and received
  Message statistics, state Established:
    InQ depth is 0
    OutQ depth is 0

                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                1          1
    Keepalives:             2          2
    Route Refresh:          0          0
    Total:                  4          4
  Default minimum time between advertisement runs is 30 seconds

 For address family: IPv4 Unicast
  Session: 7.7.7.7 session 1
  BGP table version 1, neighbor version 1/0
  Output queue size : 0
  Index 10
  10 update-group member
  Inbound soft reconfiguration allowed
                                 Sent       Rcvd
  Prefix activity:               ----       ----
    Prefixes Current:               0          0
    Prefixes Total:                 0          0
    Implicit Withdraw:              0          0
    Explicit Withdraw:              0          0
    Used as bestpath:             n/a          0
    Used as multipath:            n/a          0

                                   Outbound    Inbound
  Local Policy Denied Prefixes:    --------    -------
    Total:                                0          0
  Number of NLRIs in the update sent: max 1, min 0
  Last detected as dynamic slow peer: never
  Dynamic slow peer recovered: never

  Address tracking is enabled, the RIB does have a route to 7.7.7.7
  Connections established 10; dropped 9
  Last reset 00:00:29, due to Active open failed
  External BGP neighbor may be up to 255 hops away.
  Transport(tcp) path-mtu-discovery is enabled
  Graceful-Restart is disabled
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Connection is ECN Disabled
Mininum incoming TTL 0, Outgoing TTL 255
Local host: 8.8.8.8, Local port: 179
Foreign host: 7.7.7.7, Foreign port: 44679
Connection tableid (VRF): 0

Enqueued packets for retransmit: 0, input: 0  mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x469C4C):
Timer          Starts    Wakeups            Next
Retrans             3          0             0x0
TimeWait            0          0             0x0
AckHold             2          0             0x0
SendWnd             0          0             0x0
KeepAlive           0          0             0x0
GiveUp              0          0             0x0
PmtuAger            0          0             0x0
DeadWait            0          0             0x0
Linger              0          0             0x0

iss: 3805719326  snduna: 3805719446  sndnxt: 3805719446     sndwnd:  16265
irs: 1718523687  rcvnxt: 1718523807  rcvwnd:      16265  delrcvwnd:    119

SRTT: 99 ms, RTTO: 1539 ms, RTV: 1440 ms, KRTT: 0 ms
minRTT: 16 ms, maxRTT: 300 ms, ACK hold: 200 ms
Status Flags: passive open, gen tcbs
Option Flags: nagle, path mtu capable

Datagrams (max data segment is 1460 bytes):
Rcvd: 7 (out of order: 0), with data: 4, total data bytes: 119
Sent: 5 (retransmit: 0 fastretransmit: 0),with data: 4, total data bytes: 119


R2#

Labels:
0 Helpful
8 Replies 8

cofee
Level 5
Level 5

‎05-23-2017 09:19 PM

I noticed that you are changing default TTL value of 1 which is a default value used by EBGP to 255 "ebgp-multihop 255". You don't need to use this command to form adjacency in the given topology. You would only need to manipulate the TTL value if the ebgp neighbor is more than 1 hop away. In your case even though loopback interfaces are not directly connected, but they are local to BGP neighbors and still 1 hop away.
Command below can be used to form adjacency between these 2 routers using loopback interfaces:
neighbor 7.7.7.7 disable-connected-check
neighbor 8.8.8.8 disable-connected-check
Note - this command won't work if next hop is more than 1 hop away, in that case you will need to increase the ttl value based on placement of neighbor BGP router.

What i want to ask is how can the router 2 adjacency with router 1 without router 2 configure neighbor 7.7.7.7​ update-source loopback0 ?
If my understanding is correct you are asking how can you configure router 2 to form adjacency with router 1 without using its loopback interface address 7.7.7.7. You can use router 1 directly connected interface.

Router1:

router bgp 100
 no synchronization
 bgp router-id 7.7.7.7
 bgp log-neighbor-changes
 network 100.100.100.100 mask 255.255.255.255
 neighbor 8.8.8.8 remote-as 200
 neighbor 8.8.8.8 disable-connected-check
 no auto-summary

Router2:
router bgp 200
 no synchronization
 bgp router-id 8.8.8.8
 bgp log-neighbor-changes
 network 200.200.200.200 mask 255.255.255.255
 neighbor 1.1.1.1 remote-as 100
  no auto-summary
 
0 Helpful

williammanurung
Level 1
Level 1
In response to cofee

‎05-25-2017 05:44 AM

So, can i change the command neighbor 8.8.8.8 ebgp-multihop 255 to eighbor 8.8.8.8 ebgp-multihop 1 ? or i change to neighbor 8.8.8.8 disable-connected-check ? which one the best practice?

0 Helpful

cofee
Level 5
Level 5
In response to williammanurung

‎05-25-2017 08:04 AM

Command ebgp-multihop 1 wouldn't accomplish anything as this is the default value. By default TTL value is 1 in EBGP. meaning BGP peer is 1 hop away and this command should only be used when EBGP neighbor is more 1 hop away. In your scenario EBGP neighbor is only 1 hop and you don't need to manipulate this value.

* Below is traceroute result from R1 to R2 loopback interface that shows EBGP neighbor is 1 hop away and you will get the same result if you run a traceroute from R2 to R1 loopback address:

R1#traceroute 7.7.7.7
Type escape sequence to abort.
Tracing the route to 7.7.7.7
VRF info: (vrf in name/id, vrf out name/id)
  1 7.7.7.7 8 msec 4 msec 4 msec

The reason we have to disable directly connected check because EBGP by default verifies if the neighbor is directly connected or not. In this topology even though EBGP neighbor addresses are not directly connected, but loopback interfaces are local to EBGP neighbors and only 1 hop away. So we just need to disable that direct connect check by using this command "disable-connected-check" without manipulating ttl value.

* Here is output that shows that EBGP checks if the neighbor is directly connected or not. Look at the line highlighted in red and that's the reason we are using "disable-connected-check" command.

R1#sh ip bgp neighbors 8.8.8.8

R1#sh ip bgp neighbors 8.8.8.8
BGP neighbor is 8.8.8.8,  remote AS 200, external link
  BGP version 4, remote router ID 8.8.8.8
  BGP state = Established, up for 00:15:20

 Address tracking is enabled, the RIB does have a route to 8.8.8.8
  Connections established 1; dropped 0
  Last reset never
  External BGP neighbor not directly connected.

Below is the EBGP configuration using loopback interfaces:

R1#sh run | sec bgp
router bgp 100
 bgp log-neighbor-changes
 neighbor 8.8.8.8 remote-as 200
 neighbor 8.8.8.8 disable-connected-check
 neighbor 8.8.8.8 update-source Loopback1

R2#sh run | sec bgp
router bgp 200
 bgp log-neighbor-changes
 neighbor 7.7.7.7 remote-as 100
 neighbor 7.7.7.7 disable-connected-check
 neighbor 7.7.7.7 update-source Loopback1

Also just make sure that r1 and r2 have to route to each other's loopback interfaces. I wouldn't increase TTL value of EBGP neighbor if it is not needed and also for security reasons , basically you are saying that EBGP neighbor can be more than 1 hop away.

Just to make it clear that disable-connected-check wouldn't do anything if EBGP neighbor is more than 1 hop away "true hop" and yes in that case you would need to actually increase ebgp hop according to the placement of EBGP neighbor in the network.

0 Helpful

Georg Pauwen
VIP
VIP

‎05-24-2017 12:59 AM

Hello,

the update source is not relevant, as long as you have IP (TCP 179 actually) connectivity with the IP address you configured as the neighbor.. You have accomplished this with the static routes you added, and the ebgp-multihop.

By the way, soft reconfiguration inbound is not a good idea, since it doubles the RIB and can be a strain on your memory. BGP version 4 supports route refresh, so you don't have to do anything anymore after modifying your BGP config.

R2#sh ip bgp neighbors
BGP neighbor is 7.7.7.7, remote AS 100, external link
BGP version 4, remote router ID 7.7.7.7
BGP state = Established, up for 00:01:07
Last read 00:00:18, last write 00:00:16, hold time is 180, keepalive interval is 60 seconds
Neighbor sessions:
1 active, is not multisession capable (disabled)
Neighbor capabilities:
Route refresh: advertised and received(new)
Four-octets ASN Capability: advertised and received
Address family IPv4 Unicast: advertised and received
Enhanced Refresh Capability: advertised and received
Multisession Capability:
Stateful switchover support enabled: NO for session 1

0 Helpful

williammanurung
Level 1
Level 1
In response to Georg Pauwen

‎05-25-2017 01:02 AM

If the command neighbor 8.8.8.8 update-source Loopback0 deleted, the bgp peering not coming up.

I just confuse, why only one router configure command update-source loopback , can make up the bgp peering ?

0 Helpful

Georg Pauwen
VIP
VIP
In response to williammanurung

‎05-25-2017 01:41 AM

Hello,

neighbor 8.8.8.8 update-source Loopback0

without that line, 8.8.8.8, which is configured with the 'neighbor 7.7.7.7' command, looks for 7.7.7.7 as the neighbor, but cannot find it because you have removed that address as being the source for the updates.

0 Helpful

cofee
Level 5
Level 5
In response to williammanurung

‎05-25-2017 03:44 AM

You won't need neighbor 8.8.8.8 update-source Loopback0  command if you configure router 2 like this:

Router2:

router bgp 200
 no synchronization
 bgp router-id 8.8.8.8
 bgp log-neighbor-changes
 network 200.200.200.200 mask 255.255.255.255
 neighbor 1.1.1.1 remote-as 100
  no auto-summary
I know it's confusing that one side is using directly connected interface and the other side a loopback interface, but this was just an example based on my understanding of your question. Also wanted to show with my example that ebgp multihop is irrelevant in your configuration. Yes, ebgp multihop makes it work but that's not what needed here since both BGP speaking routers are directly connected. Just because something is working doesn't mean that's the right solution and aim should be to understand the protocol and it's requirements.
If you copy and paste the configuration that posted in my original post, BGP peering should come up.

0 Helpful

Julio E. Moisa
VIP
VIP

‎05-25-2017 08:26 AM

Hi

Your config looks fine. It would work, bgp relationship should be up and not flapping, just add, if it is GNS3 it could presents problems. 

router bgp 200, 

no synchronization
 bgp router-id 8.8.8.8
 bgp log-neighbor-changes
 network 200.200.200.200 mask 255.255.255.255
 neighbor 7.7.7.7 remote-as 100
 neighbor 7.7.7.7 update-source loopback0    

Usually if the BGP peers are directly connected you can use ebgp-multihop 2  (2 represent the number of hops to reach that IP) 

:-)




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