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BGP route map with network statement

Hi Guys

I have got a scenario where customer wants us to advertise a network via our bgp to our tier 1 providers and prepend it with AS few times so we are the secondary path....problem is route map as prepend doesnt work with network statment and work with neighbor statment....Can anyone advise if there is other way of manipulating this attribute (as path prepend) for this network ...applying route map to tier 1 provider is not an option ....is there any other clever way of manipulating this before route is advertised to tier 1...thanks in advance

regards

2 ACCEPTED SOLUTIONS

Accepted Solutions

BGP route map with network statement

I can't think of another way unless you run BGP and prepend on another route announcing that to your router that is connected to the tier 1 provider. You already have a route-map towards the tier 1 or you don't want to use one at all? In that case, why not?

Daniel Dib
CCIE #37149

Daniel Dib CCIE #37149 Please rate helpful posts.
Hall of Fame Super Blue

BGP route map with network statement

Mohammed

If i understand you correcty, you cannot use AS prepending on an IBGP route because IBGP never adds an AS to the path, only EBGP does this.

To be honest, if MED is not useful as i suggested previously, i think the more scalable, better solution is to use a route-map on the neighbor statement. If i was looking at a config that is where i would expect any AS perpending to be done.

If i have misunderstood your IBGP solution then please clarify

Jon

5 REPLIES
Hall of Fame Super Blue

Re: BGP route map with network statement

Mohammed

If you are only trying to influence the path taken from the tier 1 providers to your network then as far as i am aware you can manipulate the MED attribute with a route-map applied to the network statement. Obviously if you need to influence paths taken beyond your neighboring AS then MED is of no use.

But as you say you cannot do AS prepending. The only way to do this is with a route-map on the neighbor statement which you can't do.

Jon

BGP route map with network statement

I can't think of another way unless you run BGP and prepend on another route announcing that to your router that is connected to the tier 1 provider. You already have a route-map towards the tier 1 or you don't want to use one at all? In that case, why not?

Daniel Dib
CCIE #37149

Daniel Dib CCIE #37149 Please rate helpful posts.

BGP route map with network statement

Thanks alot Guys, just to clarify we have static route internally pointing to this subnet (subnet belongs to customer), this static route is redistributed into ospf and then ospf into bgp, i dont want to touch my tier one route maps becuase  its only one  customer and  i dont want to change setting of tier 1. i am looking for more scalable solution.....i was thinking of picking up first IBGP router who is learning this from ospf resditributioon and amending route maps where i create one for this route and as prepend and second second normal route (same route map this is already inplace) and associate this amednded route map with neighbors for it to take affect....that Way it advertise it to all the IBGP's then themIBGP's advertise it to upstream....make sense ? once again thanks....

regards

Hall of Fame Super Blue

BGP route map with network statement

Mohammed

If i understand you correcty, you cannot use AS prepending on an IBGP route because IBGP never adds an AS to the path, only EBGP does this.

To be honest, if MED is not useful as i suggested previously, i think the more scalable, better solution is to use a route-map on the neighbor statement. If i was looking at a config that is where i would expect any AS perpending to be done.

If i have misunderstood your IBGP solution then please clarify

Jon

BGP route map with network statement

Hi jon ....your right because of As loop prevention it wont allow as prepend just beofre giving update to IBGP peer....even if allowed loop prevention mechanism wont inject route in bgp table and it would fail....MED is not accepted by every isp so you run the risk of making it prefer path....so apart from as prepend which cant be applied to network statment there is no other way or update route map to tier one....well i suppose updating route is only option......there is no other way tricking bgp into making my route worse...thanks alot guys

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