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General IPv6 Topics => IPv6 Basics & Questions & General Chatter => Topic started by: Mierdin on February 02, 2011, 12:32:18 PM

Title: Default Gateway configuration
Post by: Mierdin on February 02, 2011, 12:32:18 PM
Along those lines - I know now that IPv6 determines default gateway via router advertisements - but what happens if there's two or more routers on a LAN, that could all get to my destination, but some more efficiently than others?

Another scenario is in a shared environment like a lab, some IT folk will send their traffic to one router, and another to another router for X reason....is this functionality just part of the beast that is stateless autoconfiguration, and if I want something more controlled I should use something like DHCPv6? (I hate that I just turned this into a yes or no question - elaborate if you can  ;)  )
Title: Re: Default Gateway configuration
Post by: cconn on February 02, 2011, 12:37:43 PM
Along those lines - I know now that IPv6 determines default gateway via router advertisements - but what happens if there's two or more routers on a LAN, that could all get to my destination, but some more efficiently than others?

Another scenario is in a shared environment like a lab, some IT folk will send their traffic to one router, and another to another router for X reason....is this functionality just part of the beast that is stateless autoconfiguration, and if I want something more controlled I should use something like DHCPv6? (I hate that I just turned this into a yes or no question - elaborate if you can  ;)  )

well IPv6 RA has a provision for a router preference.  RFC 4191 describes this.

From my understanding, per-destination preferred routing is not possible via RAs, but globally a router can be defined as more preferrable for hosts to utilize.
Title: Re: Default Gateway configuration
Post by: antillie on February 02, 2011, 01:48:17 PM
As long as the routers in question are exchanging routing information via something like OSPF it shouldn't really matter which router traffic is initially sent to. You could then use things like link costs, route filters, and OSPF inter-area/external area topology and such to control how traffic bound for different destinations flows across the network. The same principals can be applied to BGP, EIGRP, or static routes via things like route filters and admin distance.

If you really want to get granular with how traffic flows across your network you might want to read up on source address selection and destination address selection as defined in RFC 3484.