10-26-2021 01:50 AM
Hi,
Our Cisco 4221 routers we use, won't join the "all routers multicast group" FF02::2 after enabling ipv6 unicast-routing and configuring the interface with ipv6. Sometimes we have to disable "ipv6 unicast-routing" and enabling it again to get it work. As we use them for CCNA training, it is really annoying to help out the students without an explanation. Any advice? Known Issue?
Cisco ISR4221/K9
Cisco IOS XE Software, Version 16.09.02
pin6(config)#ipv6 unicast-routing pin6(config)#int g0/0/0 pin6(config-if)#ipv6 address 2001:db8:abcd:a::1/64 pin6(config-if)#ipv6 address fe80::1 link-local pin6(config-if)#no shut pin6#show ipv6 interface g0/0/0 GigabitEthernet0/0/0 is up, line protocol is up IPv6 is enabled, link-local address is FE80::1 No Virtual link-local address(es): Global unicast address(es): 2001:DB8:ABCD:A::1, subnet is 2001:DB8:ABCD:A::/64 Joined group address(es): FF02::1 FF02::1:FF00:1 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ICMP unreachables are sent ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds (using 30000) ND NS retransmit interval is 1000 milliseconds pin6(config)#no ipv6 unicast-routing pin6(config)#ipv6 unicast-routing pin6(config)#exit pin6# pin6# pin6#show ipv6 interface g0/0/0 *Oct 26 10:20:06.661: %SYS-5-CONFIG_I: Configured from console by console GigabitEthernet0/0/0 is up, line protocol is up IPv6 is enabled, link-local address is FE80::1 No Virtual link-local address(es): Global unicast address(es): 2001:DB8:ABCD:A::1, subnet is 2001:DB8:ABCD:A::/64 Joined group address(es): FF02::1 FF02::2 FF02::1:FF00:1
10-28-2021 01:44 AM - edited 10-28-2021 02:06 AM
Hello
ipv6 unicast -routing
int x/x
no ipv6 enable
clear ipv6 nd on-link prefix
clear ipv6 neighbours
11-09-2021 04:38 AM - edited 11-09-2021 04:39 AM
Hi Paul,
Sorry for the late response, but this doesn't help at all. I could reconstruct the problem with the Router-Advertisements. You can see that the router sends out RA's every 5 seconds and you can see that some of them doesn't include the "ICMPv6 Option (Source link-layer address: 10:b3:d6:04:d3:c0).
As soon as these Router Advertisement are received by the client, it can't resolve the IP-Address to their correspondent mac-address.
After a while a correct Router Advertisement with the including MAC address of the router interface is received, and pings are going through for 5seconds. (till another bad RA is received)!!!!
I've tested it on a cisco 1941 series router and could see that there are not that many RA's and all of them included the source link-layer address.
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