Exactly whats happening. On a couple of occasions when only 1 IP address at the far end is active for downloads we see the traffic on just one of our links because its all 1 IP to 1 IP (which was the point I was going to make...and then forgot!) instead of all 3 links. In this case its 1 BGP peering (eBGP multihop) that has 3 equal cost paths between but the principle is the same.
(we cant go per packet CEF load balancing because the far end doesn't support it - and the major traffic flow is inbound to us) Dean -----Original Message----- From: Rodney Dunn [mailto:[email protected]] Sent: 05 August 2009 21:23 To: Dean Smith Cc: Mikael Abrahamsson; Cisco Subject: Re: [c-nsp] multipath BGP not balancing equally. Ah...good one. If the sources were not random enough and it's NAT'ed to one external ip you could really be multiplexing flows with NAT. ;) Dean Smith wrote: > Would agree that volume is rare between 2xIP addresses but we have > something similair although on not quite the scale. > > We NAT a very large organisation to the Internet. They have a large > number of disparate sites that all do their own AV updates. All the PCs > download at the same time in the evening and we generate about .75 Gb/s > of traffic between our external PAT address and the AV download site for > a good couple of hours. If we had a bigger internet pipe it would be a > higher figure. (for less time of course). > > Dean > ----- Original Message ----- From: "Rodney Dunn" <[email protected]> > To: "Mikael Abrahamsson" <[email protected]> > Cc: "Cisco" <[email protected]> > Sent: Wednesday, August 05, 2009 2:19 PM > Subject: Re: [c-nsp] multipath BGP not balancing equally. > > >> For small flow combinations you are right. btw, it would be just L3 >> src/dst flows by default unless the L4 port option is enabled. >> >> I thought about there being a single flow causing the difference that >> would be hashing down one of the paths. But 2G, while not impossible, >> typically isn't used between two ip addresses. It's something to check >> though for sure. >> >> Rodney >> >> >> >> Mikael Abrahamsson wrote: >>> On Tue, 4 Aug 2009, Rodney Dunn wrote: >>> >>>> That's usually caused by routes not being the same on the paths. >>> >>> It was my understanding that this usually was caused by not having >>> enough L4 flows to loadshare on...? Ie if you have 100 TCP flows and >>> 4 paths, then it's not enough flows to get good load share on, but if >>> you instead have 10k flows and all of them are low-speed, then the >>> odds of them being equally load shared is much better? >>> >> _______________________________________________ >> cisco-nsp mailing list [email protected] >> https://puck.nether.net/mailman/listinfo/cisco-nsp >> archive at http://puck.nether.net/pipermail/cisco-nsp/ >> >> __________ NOD32 4306 (20090804) Information __________ >> >> This message was checked by NOD32 antivirus system. >> http://www.eset.com >> >> _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
