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I'm just struggling with a IPv4/IPv6 Dual Stack Setup for our new hosting environment. As central routers/switches I've got two Cisco Catalyst 3750G-48TS. The switches are not stacked, for IPv4 they are identically configured for routing and HSRP for redundancy on the first hop.

For Ipv6 I've tried to use the same configuration with routing and HSRP, but I had to learn that the Cisco switches are only able to do HSRP for IPv4 or IPv6

Now I am trying to find a working setup for IPv6 with the given equipment and I've got a couple questions:

  • IPv6 does Router advertisements and the network devices are learning these routers. How fast does the network devices mitigate a outage of a router?

  • Given that the IPv6 RA is distributing the routers, what does HSRP good to a IPv6 network?

cheerio Steve

Lairsdragon
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  • Extremely interesting question, I did not know that HSRP was bound to a ip version. Thanks for asking this, will follow closely for suggestions :) – pauska Mar 30 '11 at 11:37

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A first-hop redundancy protocol is still good to have in IPv6. While clients will automatically fail over, it will take time.

This RFC, discussing VRRP v3 (for IPv6) states in section 1.3 that it will take about 38 seconds to find the other router, if the host is doing its neighbor discovery according to defaults from the spec.

Cisco has a document covering your options, which curiously leaves out VRRP - but covers HSRP and GLBP; you'll want to review if any of these protocols will work as desired with your hardware, and get something in place if possible.. unless 38 second fail-over is ok with you!

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Shane Madden
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