Solved: Re: BGP route learning but not able to ping

Sureshbabu · ‎07-23-2023

Hello,

Pease find the below lab configuration.

R1 and R2 same AS . R3 and R4 is different AS.

i have advertise the two network

(6.6.6.6/32 & 7.7.7.7/32)

Both the network im able to ping R2 and R3. But not able to ping R4.

R4 both neighbor establish state and routes are lean in BGP.

R4#sh ip bgp 6.6.6.6
BGP routing table entry for 6.6.6.6/32, version 2
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
1
30 10
10.10.10.13 from 10.10.10.13 (3.3.3.3)
Origin IGP, localpref 100, valid, external
10
10.10.10.9 from 10.10.10.9 (2.2.2.2)
Origin IGP, localpref 100, valid, external, best
R4#sh ip bgp 7.7.7.7
BGP routing table entry for 7.7.7.7/32, version 3
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Flag: 0x820
Advertised to update-groups:
1
30 10
10.10.10.13 from 10.10.10.13 (3.3.3.3)
Origin IGP, localpref 100, valid, external
10
10.10.10.9 from 10.10.10.9 (2.2.2.2)
Origin IGP, localpref 100, valid, external, best
R4#ping 6.6.6.6

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
R4#sh ip bgp 6.6.6.6
BGP routing table entry for 6.6.6.6/32, version 2
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Advertised to update-groups:
1
30 10
10.10.10.13 from 10.10.10.13 (3.3.3.3)
Origin IGP, localpref 100, valid, external
10
10.10.10.9 from 10.10.10.9 (2.2.2.2)
Origin IGP, localpref 100, valid, external, best
R4#sh ip bgp 7.7.7.7
BGP routing table entry for 7.7.7.7/32, version 3
Paths: (2 available, best #2, table Default-IP-Routing-Table)
Advertised to update-groups:
1
30 10
10.10.10.13 from 10.10.10.13 (3.3.3.3)
Origin IGP, localpref 100, valid, external
10
10.10.10.9 from 10.10.10.9 (2.2.2.2)
Origin IGP, localpref 100, valid, external, best
R4#




R4#ping 6.6.6.6

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
....
Success rate is 0 percent (0/4)
R4#ping 7.7.7.7

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 7.7.7.7, timeout is 2 seconds:
....
Success rate is 0 percent (0/4)

R1
int fa0/1
ip add 10.10.10.1 255.255.255.252
no shut

int fa0/0
ip add 10.10.10.5 255.255.255.252
no shut

int loo1
ip add 1.1.1.1 255.255.255.255


router bgp 10
bgp router-id 1.1.1.1
no synchronization
no auto-summary
neighbor 10.10.10.6 remote-as 30
neighbor 10.10.10.2 remote-as 10

------------------------------------------
R2

int fa0/1
ip add 10.10.10.2 255.255.255.252
no shut

int fa0/0
ip add 10.10.10.9 255.255.255.252
no shut

int loo1
ip add 2.2.2.2 255.255.255.255


router bgp 10
bgp router-id 2.2.2.2
no synchronization
no auto-summary
neighbor 10.10.10.10 remote-as 40
neighbor 10.10.10.1 remote-as 10

--------------------------------------
R3

int fa0/1
ip add 10.10.10.13 255.255.255.252
no shut

int fa0/0
ip add 10.10.10.6 255.255.255.252
no shut

int loo1
ip add 3.3.3.3 255.255.255.255


router bgp 30
bgp router-id 3.3.3.3
no synchronization
no auto-summary
neighbor 10.10.10.14 remote-as 40
neighbor 10.10.10.5 remote-as 10





--------------------------------------
R4

int fa0/1
ip add 10.10.10.14 255.255.255.252
no shut

int fa0/0
ip add 10.10.10.10 255.255.255.252
no shut

int loo1
ip add 4.4.4.4 255.255.255.255


router bgp 40
bgp router-id 4.4.4.4
no synchronization
no auto-summary
neighbor 10.10.10.13 remote-as 30
neighbor 10.10.10.9 remote-as 10

Pleas suggest

MHM Cisco World · ‎07-23-2023

You need to know there is different between traffic pass through router and traffic initiate from router'

When we do ping without source we initiate traffic from router' the destiantion is add but what about source? If we dont use source with ping the router will select one interface IP' here this step make ping drop becuase the destiantion router not known this source of ping to reply. So when we initiate traffic from router always we need source (this source is know by destiantion router).

For you case you

ping 6.6.6.6

from R4 but what is source of this ping ? It can unknown by R1' when we make R4 advertise

lo 4.4.4.4

and use it as source of ping solve this issue.

View solution in original post

Flavio Miranda · ‎07-23-2023

Hi @Sureshbabu

Use

 Redistribute connect sunet

if you dont want to ender the command network repeatly times.

One router needs to tell the others routers the network it holds on its network advertisements.

Either you use the network stetament if you want to be specific or redistribute if you want to all at once.

View solution in original post

MHM Cisco World · ‎07-23-2023

You use bgp neighbor only

There is no

redistrubte connect

Nor netword <LO> mask

So bgp is run but not advertise anything

Sureshbabu · ‎07-23-2023

Hello,

Updated R1 configuration



R1#sh run | sec bgp
router bgp 10
no synchronization
bgp router-id 1.1.1.1
bgp log-neighbor-changes
network 6.6.6.6 mask 255.255.255.255
network 7.7.7.7 mask 255.255.255.255
neighbor 10.10.10.2 remote-as 10
neighbor 10.10.10.6 remote-as 30
no auto-summary
 

Loopback1 1.1.1.1 YES manual up up
Loopback2 6.6.6.6 YES manual up up
Loopback3 7.7.7.7 YES manual up up

MHM Cisco World · ‎07-23-2023

Sorry dont get what you do?

R1 have only lo 1.1.1.1 not 6.6.6.6 nor 7.7.7.7

Config each router to advertise it connect LO

MHM Cisco World · ‎07-23-2023

Note:- after each router advertise it LO use ping as following

For R1

Ping 6.6.6.6 source 1.1.1.1

Source of ping is important here to test bgp

Sureshbabu · ‎07-23-2023

Hi,

6.6.6.6 and 7.7.7.7

both network locally originated in R1.

i have advertised in BGP using network command.

in R4 both network are learning but not able to ping.

i want to know why its not able to ping

MHM Cisco World · ‎07-23-2023

Ok'

Then

In R4 advertise it LO 4.4.4.4 via bgp

From R4 do

Ping 6.6.6.6 source 4.4.4.4

Sureshbabu · ‎07-23-2023

Thank now able to ping.

Can you please more information previous why its not ping.

MHM Cisco World · ‎07-23-2023