08-30-2018 02:23 PM
Hello guys,
I have very urgent question that I need to get answer quickly.
Here is the case:
---------------------------------------------
R1
interface Ethernet0/1
ip address 10.110.160.1 255.255.255.240
router bgp 64333
bgp log-neighbor-changes
neighbor 10.10.160.1 remote-as 64222
!
address-family ipv4
bgp soft-reconfig-backup
network 10.110.160.0 mask 255.255.255.0
neighbor 10.10.160.1 activate
exit-address-family
-----------------------------------------
When I run show ip bgp in remote end I only see 0.0.0.0 that is I understand that bgp does not advertise 10.110.160.0/24. I should be able to see 10.110.160.0/24 on remote peer. The only I see advertised is when I run network 10.110.160.0 mask 255.255.255.240 under bgp, so remote peer sees 10.110.160.0/28.
Why cannot I announce /24?
Regards
Solved! Go to Solution.
08-30-2018 03:01 PM - edited 08-30-2018 03:22 PM
for 10.110.160.0/24 to be injected in BGP via the network statement, you need to have that same /24 installed in the RIB. From the config you posted, it looks like only 10.110.160.0/28 (E0/1) is present in the RIB.
If you want to advertise the /24, you could always put a static route as follow:
ip route 10.110.160.0 255.255.255.0 null 0
Regards,
08-30-2018 02:57 PM
Hello,
your 'neighbor 10.10.160.1 remote-as 64222' might only accept prefixes smaller than /24. What do you see with 'show ip bgp neighbors 10.10.160.1 advertised-routes' ?
08-30-2018 03:02 PM
This is lab environment. I have control on remote peer.
Result is nothing:
Total number of prefixes 0
This is normal as I just configured peering on remote peer.
08-30-2018 03:01 PM - edited 08-30-2018 03:22 PM
for 10.110.160.0/24 to be injected in BGP via the network statement, you need to have that same /24 installed in the RIB. From the config you posted, it looks like only 10.110.160.0/28 (E0/1) is present in the RIB.
If you want to advertise the /24, you could always put a static route as follow:
ip route 10.110.160.0 255.255.255.0 null 0
Regards,
08-30-2018 03:05 PM
Harold Ritter, is this the only way?
I am simulating real environment. 10.110.160 will be subnet bought from RIPE. So what will be real approach in that case? Assume that we got 10.110.160.0/24 from RIPE and subnetted via /28 to use for other purposes. So what will the impact if I run ip 10.110.160.0 255.255.255.0 null 0 command?
08-30-2018 03:09 PM - edited 08-30-2018 03:12 PM
If the prefix installed in the RIB does not match the network statement, BGP will simply not advertise it.
There is no real impact of configuring the static route for the /24 to null 0. Traffic falling outside the /28 will simply be sent to null0.
Regards,
08-30-2018 03:13 PM
So basically as long as I have more specific routes (as I will use other /28 ranges from /24) traffic will match with these routes and /24 set aside from routing. If so that make sense.
What if I would configure ip route 10.110.160.0 255.255.255.0 eth0/1 ?
08-30-2018 03:18 PM
> So basically as long as I have more specific routes (as I will use other /28
> ranges from /24) traffic will match with these routes and /24 set aside from
> routing. If so that make sense.
That is correct.
> "What if I would configure ip route 10.110.160.0 255.255.255.0 eth0/1 ?
Would be better to change the subnet mask to /24 on e0/1 in this case.
Regards,
08-30-2018 03:20 PM
Would be better to change the subnet mask to /24 on e0/1 in this case.
It seem correct, does not make sense to set next hop eth0/1. Thank you for your help. with static route it works.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide