Networks not connected directly not advertised in BGP

[Hasrat Raja]

Hi,

Nexus 5596 not advertising networks not connected directly, I have network statements in BGP, cleared BGP process, didn't help.

Thanks

hasrat

[Jon Marshall]

Hasrat

No much information to go on. Are these networks in the IP routing table and is there an exact match ie subnet/subnet mask between your network statement under the BGP config and the entry in the IP routing routing table ?

Jon

[Hasrat Raja]

Jon,

Thank you for the reply, these networks are not in routing table, I am not running any IGP, there is exact match under BGP.

Regards,

hasrat

[Jon Marshall]

Hasrat

When you use a "network ...." statement under BGP the router must find a match in the IP routing table or it will not be advertised. Note that it is the IP routing table not the BGP table.

If you are not running an IGP you can use statics eg.

router BGP

network 192.168.5.0 mask 255.255.255.0

now for this to be advertised there has to be an entry for this in the routing table so -

ip route 192.168.5.0 255.255.255.0  x.x.x.x  <--- where x.x.x.x is the next hop L3 device to get to that network.

To be honest if there are a lot of routes you may be better off running an IGP to exchange the routes and then you do not need to configure a lot of statics.

Jon

[Hasrat Raja]

Jon,

I added a null 0 routes & it is advertising it now, not many routes, it's a small remote location, do you think static will be  a better option ?

thanks

[Jon Marshall]

Hasrat

For a small number of routes you can use statics. But you cannot use null0 because when packets arrive at the switch they will be routed to the null0 interface ie, dropped.

Perhaps i am misunderstanding your setup but i assumed you were advertising routes from the switch via BGP for networks behind it ie. within a LAN. If so you cannot use null0 as the next hop or the packets will never leave the switch.

Perhaps you could explain your setup in a bit more detail ?

Jon

[Hasrat Raja]

Jon,

These are behind a LAN, I added following & seeing it advertised, does it need any change ?

ip prefix-list static seq 5 permit 10.166.4.0/24

!

route-map static permit 10

  match ip address prefix-list static

!

redistribute static route-map static

Thank you for all your help

[Jon Marshall]

Hasrat

i thought you were using network statements under BGP ? It looks from the above that you are redistributing statics into BGP. You can do but this is not the same as using "network ... " statements.

Which do you want to do ?

As for the null0 you can't do this. If your BGP switch advertises out 10.166.4.0 255.255.255.0 packets will then come to your switch. It will look in it's IP routing table and see that they are to be routed to null0 and it will drop them. Your static route must point to the next hop IP of the L3 device within your LAN.

I'm assuming there must be another L3 device because you said the networks were not directly connected.

Jon

[Hasrat Raja]

Jon,

sorry for the confusion, I added network statements under BGP, networks were not advertised, after adding configuration I sent or null0, I see network being advertised, I missed static route in the configuration I sent, as you pointed out this network is on another switch.

WIth static route pointing to correct destination my configuration need any change ?

thanks

[Jon Marshall · Accepted solution]

Hasrat

If you are using network statements and static routes pointing to the correct next hop IP address then it should work fine.

I'm still not sure what the config where you redistribute statics with a route map is meant to be doing ?

Jon

[Hasrat Raja]

Jon,

Just following a template, could have avoided the route map, after you pointing it out.

thanks