BGP Updating Peer

[opnsgreg]

Greetings everyone,

During a cut this weekend I wanted to aggregate our class C advertisements.

The original config was

router bgp 12345

network xx.yy.zz.0

network xx.yy.za.0

The new config was

router bgp 12345

network xx.yy.zz.0/23

My reasoning was that this syntax would advertise both of our class C's. However, when the BGP session established, while I received all external routes from the upstream peer the peer received none from me. On further examination my router was not sending updates. If I returned to the original....ie not forcing a mask...it worked. So my question is, do you have to "define" the network first before either aggregating or splitting A's, B's, or C's, or is there something else I'm missing? I would also like to advertise only 3/4 of our Class B as well but had the same issues.

Thanks,

Greg

[vladrac-ccna]

Hello,

this is quite simple

keep the first 2 networks and add

aggregate-address xx.yy.zz.0 255.255.254.0 summary-only

Vlad

[opnsgreg]

Vlad,

Thanks.....what about splitting though, ie I want to take a class B and only advertise 3/4 of it? I tried

network 123.456.0.0/17

network 123.456.128.0/18

but had the same advertisement issues (ie my router did not update the peer).

Thanks again,

Greg

[balajitvk · Accepted solution]

Hi Greg,

When u use n/w command, it will look for exact prefix in routing table until autosummary is disabled. So first u chk ur own bgp table whether the roots that u expected are there or not???

Rgs,

[opnsgreg]

Hi,

Ooh, that's making sense. The router has a static which points the entire class B to the next internal hop. So, is the best idea to turn off auto summary or replace those statics with *exactly* the same routes I want to advertise?

Thanks again,

Greg

[Richard Burts · Accepted solution]

Greg

I would suggest that you put in statics that match the prefix and mask that you want to advertise. It will work better that way.

HTH

Rick

[balajitvk]

Hi Greg,

Even u can have a static route pointing to null0 provided if u own the whole subnet u r advertising.....

Rgs,

[opnsgreg]

Thank you everyone for your replies, it really helped. I will try the statics.

Thanks again,

Greg Schaffer