Re: [isp-bgp] Hot backup

["Mostafa Ali" <mmostafa@...>]

Dear Filyurin ,

Thanks alot for your detailed reply
Actually , I have moved through the BGP conditional advertisement solution
which i prefer , however it failed as following .
the condition none-exist map which tracks the 2 prefixes ( a & b ) which
indicates that the primary peers are up worked with logic AND not OR in
other words the status only changes from withdraw to advertise only when the
2 prefixes disappears from the bgp table

I tried many configuration

1-neighbor a.a.a.a  advertise-map xx none-exist map yy
route-map yy permit 10
match ip address prefix-list a
match ip address prefix-list b

2-neighbor a.a.a.a  advertise-map xx none-exist map yy
route-map yy permit 10
match ip address prefix-list a
route-map yy permit 20
match ip address prefix-list b

3-neighbor a.a.a.a  advertise-map xx none-exist map yy
neighbor a.a.a.a  advertise-map xx none-exist map zz
route-map yy permit 10
match ip address prefix-list a
route-map yy permit 10
match ip address prefix-list b

Best Regards


----- Original Message -----
From: "Filyurin, Yan" <yan.filyurin@...>
To: <mmostafa@nile-online.net>; <isp-bgp@isp-bgp.com>
Sent: Monday, July 25, 2005 6:59 PM
Subject: RE: [isp-bgp] Hot backup


I have never done something similar before myself (even though I did
conditional advertisements) but I think you can do that -- bgp conditional
advertisements.

In other words you can do that.


Set up three BGP peering between the two routers each using the IP address
of the frame relay point to point connections.

Make sure BGP maximum-paths is configured to be at least 2

Redistribute connected interfaces into BGP of the serial links.  Make sure
something like frame relay keepalives are enabled so if something goes wrong
in the frame relay cloud, the network will disappear from BGP.

Now when configuring neighbors use conditional advertisements and the idea
behind them is that you will advertise routes over the redundant link
peering only if one or both of the prefixes for frame relay interfaces will
be suddenly gone from the BGP table.

http://www.cisco.com/warp/public/459/cond_adv.html

So you make something like this:

neighbor X.X.X.X advertise-map ADVERTISE non-exist-map NON-EXIST

ADVERTISE route map matches any IP prefix and NON-EXIST route map includes
the prefixes for the frame relay
Interfaces and that way the traffic can go on link # 3 only when one of the
links is down

The other way you can do it if you want to avoid BGP and I know even less
about it is to use object tracking and use policy routing, but I ma not sure
it is easier.  Let me know if you are more interested in that option.

If that doesn't work I am thinking how something like that could be done
with OSPF or EIGRP.

Thanks





-----Original Message-----
From: Mostafa Ali [mailto:mmostafa@...]
Sent: 25 ÉÀÌÑ 2005 Ç. 10:32
To: isp-bgp@isp-bgp.com
Subject: [isp-bgp] Hot backup

Dear All ,

I have 2 routers connected with 3 leased lines running frame-relay . all
running 2Mbps giving total of 6 Meg. My objective is to make 2 links as
primary 4 Meg while the 3rd one to be hot-backup and to carry traffic once
any of the two primary fails

could you please help me in finding suitable configuration  .

BR




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