Command by command
| Cisco IOS | Linux | What it gives you |
|---|---|---|
show ip bgp summary | birdc show protocols | All sessions and their state |
show ip bgp neighbors 10.0.1.2 | birdc show protocols all bgp1 | Full detail for one peer |
show ip bgp | birdc show route protocol bgp1 | Prefixes learned via BGP |
show ip bgp neighbors 10.0.1.2 received-routes | birdc show route protocol bgp1 filtered | Including what filters rejected |
clear ip bgp * | birdc restart bgp1 | Reset a session |
What the output looks like
$ birdc show protocols
Name Proto Table State Since Info
device1 Device --- up 12:00:00
ospf1 OSPF master4 up 12:00:04 Running
bgp1 BGP master4 up 12:00:11 EstablishedWhy the two differ
IOS folds the BGP session state and the routes it produced into one subsystem. BIRD separates them deliberately: a protocol has a state (up with Established), and separately it has an import table, an export filter and a contribution to the master routing table. This is more moving parts, but it makes a common failure visible that IOS tends to hide — a session that is perfectly established while every prefix it sent is being dropped by an import filter. show protocols shows the first; show route protocol bgp1 filtered shows the second.
The trap
A BGP protocol in state start with info Connect or Active is not established, and the two mean different things. Connect means BIRD is trying to open the TCP session. Active means the TCP attempt failed and it is waiting to retry — which points at reachability or port 179 being blocked, not at BGP configuration. Confusingly, Active is the more broken of the two despite sounding healthier.
Common questions
Why is my BGP session stuck in Active?
Almost always TCP, not BGP. Either the peer is unreachable, or something is blocking port 179 between you. Test with ping to the peer address and then a TCP probe to port 179 before touching any BGP configuration.
How do I see the AS path for a prefix?
birdc show route all <prefix>. The plain show route output gives you the prefix and next hop; all adds the BGP attributes including the AS path, local preference and communities.
Stop reading, start running
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