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Beginner

Can the lifetime of default route (in RA) to the client be renewed?

The question is that why the "lifetime" for the "ipv6 nd ra" is set maximum 1800sec? It equals to just 30mins.

If this timer is expired, how to renew the RA to the client? If the renewal is not possible, the client will loss the default

route information forever. What is the solution for client not loss the default route (except the manual configuration)?

Thank you

7 REPLIES 7
Cisco Employee

Can the lifetime of default route (in RA) to the client be renew

Hi,

It's not really a lifetime at such. A non zero value means this router can be considered as a default-gateway.

From RFC 4861:

"

 Router Lifetime
                     16-bit unsigned integer.  The lifetime associated
                     with the default router in units of seconds.  The
                     field can contain values up to 65535 and receivers
                     should handle any value, while the sending rules in
                     Section 6 limit the lifetime to 9000 seconds.  A
                     Lifetime of 0 indicates that the router is not a
                     default router and SHOULD NOT appear on the default
                     router list.  The Router Lifetime applies only to
                     the router's usefulness as a default router; it
                     does not apply to information contained in other
                     message fields or options.  Options that need time
                     limits for their information include their own
                     lifetime fields.

"

Also please refer to http://www.cisco.com/en/US/docs/ios/ipv6/command/reference/ipv6_07.html#wp2360344

HTH

Laurent.

Beginner

Re: Can the lifetime of default route (in RA) to the client be r

Thanks.

The lifetime in this case is just notify the client that this route can be considered as a default route. The reason to ask the question is because it is related to the following issue.

To setup a ISATAP tunnel, ISATAP server should send RA (a prefix) with a non-zero lifetime to the client, so that the client will treat this route as default route. Once the tunnel is built up, the default route pointing to server is available. But after the lifetime, the route disappears and never come back. How to figure this out?

Cisco Employee

Re: Can the lifetime of default route (in RA) to the client be r

Hi Lisa,

Once the RA received and processed, the host will create an entry in its default-router list. For each entry it will associate a timer set to the same value as the "router lifetime". If no RA are received to refresh this entry, then it is deleted.

So my guess is either your RA interval on the server is higher than the router lifetime or you have another issue which prevent the client to receive the RA.

HTH

Laurent.

Beginner

Re: Can the lifetime of default route (in RA) to the client be r

Hi Laurent,

The thing is client has received the RA as a default route. The RA interval time and lifetime are set according to the rule (interval time

Thank you

Cisco Employee

Re: Can the lifetime of default route (in RA) to the client be r

Are you sure the client is receiving and well processing the RA every RA-Interval ? If it's the case there may be a bug on the client side.

Beginner

Re: Can the lifetime of default route (in RA) to the client be r

I am not clear about the relationship between RA-interval and RA-lifetime. Is it true that RA will be sent every RA-interval to Client within RA-lifetime? So, when the RA-lifetime is expired, the RA-interval will not be functional any more. If this is ture, the problem is nothing to do with RA-interval. Instead, it is all about RA-lifetime. Am I right? By the way, I use cisco router to simulate the client. The configuration is done following the document

http://docwiki.cisco.com/wiki/IPv6_ISATAP_configuration_example_with_a_Cisco_router_as_a_client

Thank you for your quick response.

Cisco Employee

Re: Can the lifetime of default route (in RA) to the client be r

You should received a RA every RA_Interval, Once it's received it will refresh the entry in the Default router list assuming the router lifetime is different from 0. There is timer associated to this entry which is equal to the router lifetime value embedded in the RA. This timer is reset each time a RA is received. If this timer expired (no RA received) then the entry is deleted. If later a RA is received, the entry should be created again.

If you are sure the client is receiving the RA every RA-Interval then open a TAC case to have more support. Unfortunately I don't have time right now to test it (maybe in the coming week).

HTH

Laurent.

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