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jamie.orzechowski@gmail.com 06-26-2007 06:24 PM

iBGP Questions
 
I am new to BGP and have a few question with iBGP

here is the current setup

RouterA - eBGP session to one of our upstream1
RouterA - iBGP to RouterB

RouterB - iBGP to RouterA

For some reason RouterB is not recieving any routes from RouterA via
iBGP.

If I show the bgp table on RouterB it is empty yet the iBGP session is
established correctly.

Any ideas?


Trendkill 06-26-2007 06:34 PM

Re: iBGP Questions
 
On Jun 26, 2:24 pm, jamie.orzechow...@gmail.com wrote:
> I am new to BGP and have a few question with iBGP
>
> here is the current setup
>
> RouterA - eBGP session to one of our upstream1
> RouterA - iBGP to RouterB
>
> RouterB - iBGP to RouterA
>
> For some reason RouterB is not recieving any routes from RouterA via
> iBGP.
>
> If I show the bgp table on RouterB it is empty yet the iBGP session is
> established correctly.
>
> Any ideas?


IBGP will only advertise networks that are in an underlying IGP,
including static routes. What other protocol or static routes do you
have in place? Else Router A will not be advertising anything to
Router B as those routes are not in an underlying interior protocol.


Trendkill 06-26-2007 06:34 PM

Re: iBGP Questions
 
On Jun 26, 2:34 pm, Trendkill <jpma...@gmail.com> wrote:
> On Jun 26, 2:24 pm, jamie.orzechow...@gmail.com wrote:
>
>
>
> > I am new to BGP and have a few question with iBGP

>
> > here is the current setup

>
> > RouterA - eBGP session to one of our upstream1
> > RouterA - iBGP to RouterB

>
> > RouterB - iBGP to RouterA

>
> > For some reason RouterB is not recieving any routes from RouterA via
> > iBGP.

>
> > If I show the bgp table on RouterB it is empty yet the iBGP session is
> > established correctly.

>
> > Any ideas?

>
> IBGP will only advertise networks that are in an underlying IGP,
> including static routes. What other protocol or static routes do you
> have in place? Else Router A will not be advertising anything to
> Router B as those routes are not in an underlying interior protocol.


http://www.ubookcase.com/book/Cisco/...2lev1sec4.html


Chris 06-26-2007 07:23 PM

Re: iBGP Questions
 
On Tue, 26 Jun 2007 18:34:28 -0000, Trendkill wrote:

> On Jun 26, 2:24 pm, jamie.orzechow...@gmail.com wrote:
>> I am new to BGP and have a few question with iBGP
>>
>> here is the current setup
>>
>> RouterA - eBGP session to one of our upstream1
>> RouterA - iBGP to RouterB
>>
>> RouterB - iBGP to RouterA
>>
>> For some reason RouterB is not recieving any routes from RouterA via
>> iBGP.
>>
>> If I show the bgp table on RouterB it is empty yet the iBGP session is
>> established correctly.
>>
>> Any ideas?

>
> IBGP will only advertise networks that are in an underlying IGP,
> including static routes. What other protocol or static routes do you
> have in place? Else Router A will not be advertising anything to
> Router B as those routes are not in an underlying interior protocol.


With synchronization on this is certainly true. However you don't want
this. If router A is receiving routes from the internet then of course you
don't want a full internet routing table in your IGP!

Make sure that your iBGP config between A and B have;

no synchronization
update-source Loopback0 (your IGP should provide routing between loopbacks)
next-hop-self (so that when router A sends a BGP route to B it changes the
next-hop and B won't have a connection to the transit provider)

I think that the key here is synchronization.

Can you provide your BGP configs?

Chris.

Trendkill 06-26-2007 07:30 PM

Re: iBGP Questions
 
On Jun 26, 3:23 pm, Chris <mandrake...@hotmail.com> wrote:
> On Tue, 26 Jun 2007 18:34:28 -0000, Trendkill wrote:
> > On Jun 26, 2:24 pm, jamie.orzechow...@gmail.com wrote:
> >> I am new to BGP and have a few question with iBGP

>
> >> here is the current setup

>
> >> RouterA - eBGP session to one of our upstream1
> >> RouterA - iBGP to RouterB

>
> >> RouterB - iBGP to RouterA

>
> >> For some reason RouterB is not recieving any routes from RouterA via
> >> iBGP.

>
> >> If I show the bgp table on RouterB it is empty yet the iBGP session is
> >> established correctly.

>
> >> Any ideas?

>
> > IBGP will only advertise networks that are in an underlying IGP,
> > including static routes. What other protocol or static routes do you
> > have in place? Else Router A will not be advertising anything to
> > Router B as those routes are not in an underlying interior protocol.

>
> With synchronization on this is certainly true. However you don't want
> this. If router A is receiving routes from the internet then of course you
> don't want a full internet routing table in your IGP!
>
> Make sure that your iBGP config between A and B have;
>
> no synchronization
> update-source Loopback0 (your IGP should provide routing between loopbacks)
> next-hop-self (so that when router A sends a BGP route to B it changes the
> next-hop and B won't have a connection to the transit provider)
>
> I think that the key here is synchronization.
>
> Can you provide your BGP configs?
>
> Chris.


I'm not saying turn up the whole internet routing table in an IGP, but
simply summarize into a default route, or make sure that whatever
networks you are pushing into IBGP are being advertised via an IGP.
Sychronization will not fix the requirement for an IGP I don't believe.


Trendkill 06-26-2007 07:34 PM

Re: iBGP Questions
 
On Jun 26, 3:30 pm, Trendkill <jpma...@gmail.com> wrote:
> On Jun 26, 3:23 pm, Chris <mandrake...@hotmail.com> wrote:
>
>
>
> > On Tue, 26 Jun 2007 18:34:28 -0000, Trendkill wrote:
> > > On Jun 26, 2:24 pm, jamie.orzechow...@gmail.com wrote:
> > >> I am new to BGP and have a few question with iBGP

>
> > >> here is the current setup

>
> > >> RouterA - eBGP session to one of our upstream1
> > >> RouterA - iBGP to RouterB

>
> > >> RouterB - iBGP to RouterA

>
> > >> For some reason RouterB is not recieving any routes from RouterA via
> > >> iBGP.

>
> > >> If I show the bgp table on RouterB it is empty yet the iBGP session is
> > >> established correctly.

>
> > >> Any ideas?

>
> > > IBGP will only advertise networks that are in an underlying IGP,
> > > including static routes. What other protocol or static routes do you
> > > have in place? Else Router A will not be advertising anything to
> > > Router B as those routes are not in an underlying interior protocol.

>
> > With synchronization on this is certainly true. However you don't want
> > this. If router A is receiving routes from the internet then of course you
> > don't want a full internet routing table in your IGP!

>
> > Make sure that your iBGP config between A and B have;

>
> > no synchronization
> > update-source Loopback0 (your IGP should provide routing between loopbacks)
> > next-hop-self (so that when router A sends a BGP route to B it changes the
> > next-hop and B won't have a connection to the transit provider)

>
> > I think that the key here is synchronization.

>
> > Can you provide your BGP configs?

>
> > Chris.

>
> I'm not saying turn up the whole internet routing table in an IGP, but
> simply summarize into a default route, or make sure that whatever
> networks you are pushing into IBGP are being advertised via an IGP.
> Sychronization will not fix the requirement for an IGP I don't believe.


I obviously am sleeping at the wheel today. Synchronization should
relieve the IGP requirement....although I still recommend an
underlying IGP.


Chris 06-26-2007 09:07 PM

Re: iBGP Questions
 
On Tue, 26 Jun 2007 19:34:12 -0000, Trendkill wrote:

> On Jun 26, 3:30 pm, Trendkill <jpma...@gmail.com> wrote:
>> On Jun 26, 3:23 pm, Chris <mandrake...@hotmail.com> wrote:
>>
>>
>>
>>> On Tue, 26 Jun 2007 18:34:28 -0000, Trendkill wrote:
>>> > On Jun 26, 2:24 pm, jamie.orzechow...@gmail.com wrote:
>>> >> I am new to BGP and have a few question with iBGP

>>
>>> >> here is the current setup

>>
>>> >> RouterA - eBGP session to one of our upstream1
>>> >> RouterA - iBGP to RouterB

>>
>>> >> RouterB - iBGP to RouterA

>>
>>> >> For some reason RouterB is not recieving any routes from RouterA via
>>> >> iBGP.

>>
>>> >> If I show the bgp table on RouterB it is empty yet the iBGP session is
>>> >> established correctly.

>>
>>> >> Any ideas?

>>
>>> > IBGP will only advertise networks that are in an underlying IGP,
>>> > including static routes. What other protocol or static routes do you
>>> > have in place? Else Router A will not be advertising anything to
>>> > Router B as those routes are not in an underlying interior protocol.

>>
>>> With synchronization on this is certainly true. However you don't want
>>> this. If router A is receiving routes from the internet then of course you
>>> don't want a full internet routing table in your IGP!

>>
>>> Make sure that your iBGP config between A and B have;

>>
>>> no synchronization
>>> update-source Loopback0 (your IGP should provide routing between loopbacks)
>>> next-hop-self (so that when router A sends a BGP route to B it changes the
>>> next-hop and B won't have a connection to the transit provider)

>>
>>> I think that the key here is synchronization.

>>
>>> Can you provide your BGP configs?

>>
>>> Chris.

>>
>> I'm not saying turn up the whole internet routing table in an IGP, but
>> simply summarize into a default route, or make sure that whatever
>> networks you are pushing into IBGP are being advertised via an IGP.
>> Sychronization will not fix the requirement for an IGP I don't believe.

>
> I obviously am sleeping at the wheel today. Synchronization should
> relieve the IGP requirement....although I still recommend an
> underlying IGP.


With a BGP network you only need an IGP for each iBGP neighbor to be able
to see each other in order to set up iBGP sessions. This is because they
usually use the loopback addresses and are not always directly connected
neighbors. As far as advertising BGP routes goes, synchronization should be
off and you don't need to see any external routes in the IGP, just BGP.

He obviously has his BGP sessions set up so routing between A and B isn't
an issue so I suspect that he has synchronization on. I've set up plenty of
iBGP peers and never had issues with them receiving routes from other peers
and full routes from our edge routers .. and our iBGP config is VERY
simple. Nothing clever going on!

Router bgp 12345
no synchronization
bgp log-neighbor changes
neighbor LOCAL peer-group
neighbor LOCAL remote-as 12345
neighbor LOCAL update-source Loopback0
neighbor LOCAL next-hop-self
neighbor x.x.x.x peer-group LOCAL
neighbor x.x.x.x description iBGP to something or other
neighbor x.x.x.x password 7 blahblahvlah

Works like a charm. There's no redistribution between BGP and our IGP
(IS-IS) at all.

Chris.


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