Scenario:
You are a network engineer responsible for the network for a local fighting tournament. Two of the fighters exchange tactics using BGP to advertise the networks. They don’t want to exchange everything they know so they are a number of inbound route filters. You want to make sure the new filters are applied without resetting the BGP peering…get over here!
Goal:
- All IP addresses have been preconfigured for you.
- Configure EBGP between AS1 and AS2.
- Advertise network 2.2.2.0 /24 on router Scorpion in BGP.
- Configure a prefix-list on router SubZero that filters network 2.2.2.0 /24 and apply it to neighbor router Scorpion.
- Ensure the changes are visible without resetting the BGP peering.
IOS:
c3640-jk9s-mz.124-16.bin
Topology:
Video Solution:
Configuration Files
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Written by René Molenaar - CCIE #41726
excellent lab.
deceptively simple, but if you dig, there is a lot to research here.
spurred me to look up the difference between “route refresh” capability
and the received routes from the bgp neighbor “soft-reconfiguration inbound”.
=
with NO “soft-reconfiguration inbound”:
SubZero#clear ip bgp 192.168.12.2 in
BGP: 192.168.12.2 sending REFRESH_REQ(5) for afi/safi: 1/1
BGP: 192.168.12.2 send message type 5, length (incl. header) 23
SubZero#clear ip bgp 192.168.12.2 soft in
BGP: 192.168.12.2 sending REFRESH_REQ(5) for afi/safi: 1/1
BGP: 192.168.12.2 send message type 5, length (incl. header) 23
where as WITH “soft-reconfiguration inbound”:
there is NO debug output for either
– clear ip bgp 192.168.12.2 in
– clear ip bgp 192.168.12.2 soft in
this seems to imply this disables, or perhaps more aptly,
it preempts the negotiated “route refresh” bgp capability.
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it seems one way to verify the old “soft-reconfiguration inbound”
is to issue the “show ip bgp neighbor X.X.X.X received-routes” command.
with NO “soft-reconfiguration inbound”:
SubZero#sh ip bgp neighbor 192.168.12.2 received-routes
% Inbound soft reconfiguration not enabled on 192.168.12.2
where as WITH “soft-reconfiguration inbound”:
SubZero#sh ip bgp neighbor 192.168.12.2 received-routes | b Net
Network Next Hop Metric LocPrf Weight Path
* 2.2.2.0/24 192.168.12.2 0 0 2 i
Total number of prefixes 1
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excerpt from Cisco command refrence:
If all BGP routers support the route refresh capability, use the “clear ip bgp ipv4”
command with the “in” keyword.
You need not use the “soft” keyword, because soft reset is automatically assumed when
the route refresh capability is supported.
good lab 🙂
Simple but very useful! thanks Rene. This site is helping me alot!
Nice lab, thanks!