BGP Route Announcemnt

[safe]

Dear all,

We have 10 Ip block of class C .We have taken Internet BW from 2 service providers.We had advertises some Ip block on ISP1 & some on ISP 2 but probs is that Ip Block we have Advertises on ISP 1 for that traffice coming from outside to our network is coming thr' Internet link of ISP2. So that it is difficult for us to share Internet Load though we have sufficient internet BW .

Is there any solution in which we can advertise only limited class like 224,240,252 subnet on particular ISP so that which customer subscribe more BW should get require BW. Also is there any way to control BGP Incoming traffic.

For Outgoing traffic we are using Default Routes .We have define route-map to advertise Ip blocks on Upstream providers.

Thanks

SAM

[Georg Pauwen]

Hello Sam,

are your routers, the ones connected to both ISPs, running BGP amongst them ? If so, you could use the MED or AS-PATH attributes to influence the way traffic enters your AS...

Regards,

GP

[safe]

Thks for reply GP,

Our router is connected to both ISP,running BGP for both providers .How can we use MED if my upstream providers already set local preference in there network.

Thks

SAM

[ruwhite]

You can't.... First, MED won't win against local prefs. Second, if you are connecting to multiple providers, the MEDs won't have any impact, anyway. The only real options are to use as path prepend to adjust the as path length--and this is crude, and doesn't always work--or to use communities to influence your SP's local preference.

Take a look at RFC1998 for information on using communities to influence your SP's local preference.

:-)

Russ.W

[Adam Frederick]

I may be missing something, but I thought local preference wasn't advertised by EBGP peers? Help me understand what I'm missing.

[ruwhite]

RFC1998 describes a mechanism where you set communities on outbound routes towards your SP's, and the SP's use those communities to set their local preference back towards your network. You can't send local preference to an eBGP peer, but, if you service provider implements RFC1998 functionality, you can influence their choice of local preference away from their defaults, and towards something that makes your inbound traffic more even, possibly.

:-)

Russ.W

[Harold Ritter]

Another option to control ingress traffic would be to use conditional advertisement.

For more information on conditional advertisement, refer to the following document:

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

Hope this helps,

[mesuti]

Try the following to gain an symmetric traffic between your ISPs. First group all the Class C blocks on one prefix and advertise this to both ISPs, then separate 5 Class Cs and advertise them just to lets say ISP A, and filter them to the other ISP on outbound. Advertise the other half of the Class C addresses to the ISP B and filter the first 5 Class Cs. And the first 5 blocks will always come through ISP A and other ones through ISP B. And it is fault tolerant because of the aggregate route we advertised to both ISPs. If you want detailed explanation just let me know.

hope it helps

Best Regards

Mesut Abdurrahmani