BGP and OSPF Asymmetry
Bookmark this page:
 Yahoo!
 Google
 Windows Live
 del.icio.us
 digg
 Netscape
|
|
|||||||||||||||||||
|
Posted by Darren Green on September 5, 2008, 8:28 am
Please log in for more thread options I have a network where I have traffic coming in from various AS No's into a Core AS call it AS 100. At the bottom end I have 2 x links out of AS 100 into a Co-Lo using a private AS 65001. All remote AS's have to traverse AS 100 to reach my Co-Lo. In my Co-Lo I have 4 x routers. The WAN element (2 x routers) connects AS65001 to AS100. On the inside of my WAN routers I have LAN connections to a pair of 6509's (one is active for all HSRP addresses). The connections between WAN and LAN devices are crossed over so each WAN router connects to each 6509. These connections are configured as /30 links. There is no iBGP internally just equal cost path OSPF links. My problem is that OSPF is set to load share traffic back out to the remote locations. As traffic can come in down either WAN link, how can I get OSPF to route it back the same way. I need a way to tag routes coming into AS100 differently based on my own scheme but route-maps don=92t allow this. How can I ensure that OSPF understands which BGP route my traffic has entered on, to allow it to route back the same way. If I can=92t find the answer I will just have to live with the probability of asymmetric traffic. Regards Darren | |||||||||||||||||||
|
Posted by fugettaboutit on September 5, 2008, 10:19 am
Please log in for more thread options Darren Green wrote: Maybe I don't have a full picture of what you're doing, but does the asymmetry matter? Are you transporting voice traffic? If I understand, you want the internal WAN links to send the return packets of a given flow over the same ingress pipe (from the co-lo's perspective). I'd say that if it is an issue of transporting traffic that would be sensitive to reordering, perhaps ensuring per-flow switching would be the way to go. Otherwise, I'm not sure worrying about the return trip is an issue unless you have some other management policy you need to adhere to, or as I just mentioned, packet reordering (non-TCP) is of concern Sorry if I totally misunderstood the issue! Good Luck! | |||||||||||||||||||
|
Posted by Darren Green on September 5, 2008, 4:50 pm
Please log in for more thread options
>>
>> I need a way to tag routes coming into AS100 differently based on my >> own scheme but route-maps don’t allow this. How can I ensure that OSPF >> understands which BGP route my traffic has entered on, to allow it to >> route back the same way. If I can’t find the answer I will just have >> to live with the probability of asymmetric traffic. >> >> Regards >> >> Darren >
> Maybe I don't have a full picture of what you're doing, but does the > asymmetry matter? Are you transporting voice traffic? If I understand, > you want the internal WAN links to send the return packets of a given > flow over the same ingress pipe (from the co-lo's perspective). I'd say > that if it is an issue of transporting traffic that would be sensitive > to reordering, perhaps ensuring per-flow switching would be the way to > go. Otherwise, I'm not sure worrying about the return trip is an issue > unless you have some other management policy you need to adhere to, or > as I just mentioned, packet reordering (non-TCP) is of concern > > Sorry if I totally misunderstood the issue! > > Good Luck! > Thanks for the response. You were spot on in your understanding. I had sort of got to the point that the asymmetric traffic would be OK, I suppose many networks have such an element anyway. Just wanted to avoid it if possible. There is no voice at present but there is some Citrix which I believe will be OK in this type of environment. If voice comes along I will likely do some prepending and OSPF manipulation to ensure that the traffic routes in and out the way I want it. Kind regards Darren | |||||||||||||||||||
| Similar Threads | Posted |
| BGP and OSPF Asymmetry | September 5, 2008, 8:28 am |
| BGP routing asymmetry | July 5, 2005, 1:44 pm |
| Re: basic/weird ospf question- ospf gurus need help!!! | December 11, 2007, 4:31 am |
| ospf | February 6, 2006, 11:17 am |
| ospf | March 2, 2006, 8:29 pm |
| OSPF | March 2, 2006, 8:53 pm |
| Useful OSPF Q & A | August 24, 2006, 7:50 am |
| OSPF behind a PIX | June 29, 2005, 12:01 pm |
| ospf | June 30, 2005, 1:38 pm |
| OSPF or BGP | January 9, 2007, 2:15 pm |
| Ospf in VRF | April 2, 2007, 4:41 am |
| ospf on css | April 21, 2008, 5:16 pm |
| EIGRP and OSPF | July 24, 2005, 11:42 pm |
| ospf over mpls | August 29, 2005, 7:15 am |
| OSPF over GRE Tunnels | September 25, 2005, 2:25 pm |
> into a Core AS call it AS 100.
>
> At the bottom end I have 2 x links out of AS 100 into a Co-Lo using a
> private AS 65001. All remote AS's have to traverse AS 100 to reach my
> Co-Lo.
>
> In my Co-Lo I have 4 x routers. The WAN element (2 x routers) connects
> AS65001 to AS100. On the inside of my WAN routers I have LAN
> connections to a pair of 6509's (one is active for all HSRP
> addresses). The connections between WAN and LAN devices are crossed
> over so each WAN router connects to each 6509. These connections are
> configured as /30 links. There is no iBGP internally just equal cost
> path OSPF links.
>
> My problem is that OSPF is set to load share traffic back out to the
> remote locations. As traffic can come in down either WAN link, how can
> I get OSPF to route it back the same way.
>
> I need a way to tag routes coming into AS100 differently based on my
> own scheme but route-maps don’t allow this. How can I ensure that OSPF
> understands which BGP route my traffic has entered on, to allow it to
> route back the same way. If I can’t find the answer I will just have
> to live with the probability of asymmetric traffic.
>
> Regards
>
> Darren