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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>How do providers typically implement routing for multiple LNSs (terminating ADSL user sessions)? Given that a set of LNSes could be carrying many (thousands?) of host routes (or small subnets), is it preferable to integrate them directly into iBGP for scalability, or isolate them and run an IGP and perform some redistribution at (say) a redundant pair of LNS aggregation routers? <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I can see good scalability arguments for iBGP (and it is said to be good practice to keep customer prefixes in iBGP), but would be concerned over the BGP churn and hence convergence for large numbers of injected and withdrawn routes (e.g. user sessions reconnecting and/or moving between LNSs).<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>An IGP (e.g. OSPF NSSA) could potentially converge much quicker in a similar scenario but perhaps doesn't scale as well as iBGP. The problem is less of a concern if each LNS only has its own pool of address from which dynamic users are allocated addresses (as the summarisation placement is more obvious), but it's not so clear when there are many users with static addresses or require more that a single static address.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Cheers,<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>Matt<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal>-- <o:p></o:p></p><p class=MsoNormal>Matthew Melbourne<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>