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)?
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
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?
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.
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
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.
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
Thank you for your quick response.
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).