08-29-2025 07:16 AM - edited 08-29-2025 07:18 AM
So i have the following topology-
ISP-RT-1 has a default route pointing to 192.168.20.1
Image being used is - vios-adventerprise9-m.SPA.159-3.M6
Some show commands-
ISP-RT-1#show ip bgp 0.0.0.0
BGP routing table entry for 0.0.0.0/0, version 2
Paths: (1 available, best #1, table default)
Advertised to update-groups:
3
Refresh Epoch 1
Local
192.168.20.1 from 0.0.0.0 (1.1.1.1)
Origin IGP, metric 0, localpref 100, weight 32768, valid, sourced, local, best
rx pathid: 0, tx pathid: 0x0
Now im trying to aadvertise this to the 3 ibgp peers (1 of them not shown in the pic but its just a direct point to point) and it doesnt work at all-
ISP-RT-1#show running-config | section bgp
router bgp 65312
bgp log-neighbor-changes
network 0.0.0.0
neighbor 65.30.24.1 remote-as 65312
neighbor 65.30.24.5 remote-as 65312
neighbor 65.30.24.9 remote-as 65312
ISP-RT-1#show ip bgp summary
BGP router identifier 1.1.1.1, local AS number 65312
BGP table version is 2, main routing table version 2
1 network entries using 144 bytes of memory
1 path entries using 84 bytes of memory
1/1 BGP path/bestpath attribute entries using 160 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 388 total bytes of memory
BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
65.30.24.1 4 65312 9 10 2 0 0 00:04:59 0
65.30.24.5 4 65312 9 11 2 0 0 00:04:49 0
65.30.24.9 4 65312 9 11 2 0 0 00:04:37 0
If i look at the routing table on say ISP-RT-2 it doesnt learn the default route, what am i doing wrong?
ISP-RT-2#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR
Gateway of last resort is not set
2.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 2.2.2.0/24 is directly connected, Loopback0
L 2.2.2.2/32 is directly connected, Loopback0
65.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 65.30.24.0/30 is directly connected, GigabitEthernet0/1
L 65.30.24.1/32 is directly connected, GigabitEthernet0/1
Its the same on the other 2 routers as well and they do not learn the default route, so yeah no idea whats going on.
Ive researched online and everywhere i look they say all i need is a "network 0.0.0.0" statement which i tried as you can see but yeah doesnt work.
Thank You
Solved! Go to Solution.
09-01-2025 01:19 AM
from CCIE v5 vol. 2 by Narbik, Vinston, Cisco Press.
Regards, ML
**Have fun labbing!!!***
***Please Rate All Helpful Responses ***
09-01-2025 04:03 PM
08-29-2025 07:18 AM
You need to use defualt information originate under bgp.
MHM
08-29-2025 07:19 AM
so yeah i tried that too and it doesnt work, could it have something to do with the image im using? i do have a csr1000v image as well which i can use.
08-29-2025 07:22 AM
Bgp advertise 0.0.0.0 only if this appear in RIB
Can i see
Show ip route
MHM
08-29-2025 07:26 AM
yes it does have it-
ISP-RT-1#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
a - application route
+ - replicated route, % - next hop override, p - overrides from PfR
Gateway of last resort is 192.168.20.1 to network 0.0.0.0
S* 0.0.0.0/0 [254/0] via 192.168.20.1
1.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 1.1.1.0/24 is directly connected, Loopback0
L 1.1.1.1/32 is directly connected, Loopback0
65.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C 65.30.24.0/30 is directly connected, GigabitEthernet0/1
L 65.30.24.2/32 is directly connected, GigabitEthernet0/1
C 65.30.24.4/30 is directly connected, GigabitEthernet0/2
L 65.30.24.6/32 is directly connected, GigabitEthernet0/2
C 65.30.24.8/30 is directly connected, GigabitEthernet0/3
L 65.30.24.10/32 is directly connected, GigabitEthernet0/3
192.168.20.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.20.0/24 is directly connected, GigabitEthernet0/0
L 192.168.20.106/32 is directly connected, GigabitEthernet0/0
08-29-2025 07:28 AM
192.168.20.1 <<- this IP reachable via other ibgp neighbors
MHM
08-29-2025 07:30 AM
If this IP not know
Use next-hop self
Abd network 0.0.0.0 under bgp
MHM
08-29-2025 07:30 AM
ah ok ill try next hop self
08-29-2025 07:28 AM
Hello @kbk989
Because the static default is not present in the routing table, the network 0.0.0.0 statement in BGP has no effect...
=> so nothing is advertised to your iBGP peers.
08-29-2025 07:31 AM
i see makes sense
08-29-2025 09:40 AM
Still not get defualt in ibgp?
MHM
08-29-2025 09:47 AM
Show ip bgp neighbors x.x.x.x advertise <<- share this in router
Show ip bgp neighbors x.x.x.x receive <<- share this in remote router
Share debug ip bgp update after you clear ip bgp process for both router and remote one
MHM
08-29-2025 09:38 AM
is it working now? Book by W. Odom CCIE v4 RS has a summary table that shows 3 ways to advertised default route under bgp. I recommend his book. (topic replicated into CCIE v5 RS book I think)
Regards, ML
**Have fun labbing!!!***
***Please Rate All Helpful Responses ***
08-29-2025 10:09 AM
next hop issue how I know that ?
ISP-RT-1#show ip bgp 0.0.0.0
BGP routing table entry for 0.0.0.0/0, version 2
Paths: (1 available, best #1, table default)
Advertised to update-groups:
3
Refresh Epoch 1
Local
192.168.20.1 from 0.0.0.0 (1.1.1.1)
Origin IGP, metric 0, localpref 100, weight 32768, valid, sourced, local, best
rx pathid: 0, tx pathid: 0x0
solution is next hop self
NOTE:- use debug ip bgp update next time in trouble
NOTE:- clear ip bgp <<- when you add or remove any command of BGP
MHM
08-31-2025 04:04 AM
other solution
use
neighbour x.x.x.x default-information <<- under R2 (router have static default route)
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