Just how many ipv6 prefixes can be advertisd in ICMPv6-RA ( cisco switch ) ?

I was really bored today,  so I enabled some ipv6 interfaces on a cisco 6509-E switch and cisco 2960S switch. Just to see how may ipv6 route-advertisement can be inserted for autoconf.

My outcome was a big surprise. Most unix and windows systems can take upto 15 max ipv6-prefixes.
Will  the cisco 2960S with auto config , can take much more, but 1st here's the cfg.

And on the  cisco 6509-E,  I decided to inject  100 prefixes on my  interface. I used  a cfgmaker to speed up my configuration;

Now we enabled debug to monitor the ipv6 ND RAs

 debug ipv6 nd was used for ipv6 prefixes diagnostics






Only 44 prefixes assigned on my  vlan9 interface from  the cisco 6509-E where sent.  So out of the 100 prefixes, we've only had autconf  configure 44. Than the  2960S threw up an error via the ipv6 address manager.

So does a limitation exists  in the number of ipv6 prefixes that can be advertised via a cisco L3 switch?   I used tshark to confirm just how many prefixes are  being sent out of the 100 that was enabled on my ipv6 interface & it confirms 44 prefixes where advertised by the L3 cisco switch.
A local debug on RA-enabled  L3 switch shows 44 ipv6 prefixes being sent also;

Aug  4 15:00:39.699: ICMPv6-ND: Request to send RA for FE80::1EE6:C7FF:FE52:A6C0
Aug  4 15:00:39.699: ICMPv6-ND: Setup RA from FE80::1EE6:C7FF:FE52:A6C0 to FF02::1 on Vlan9
Aug  4 15:00:39.699: ICMPv6-ND:  MTU = 1500
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:1::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:2::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:3::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:4::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:5::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:6::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:7::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:8::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:9::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:10::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:11::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:12::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:13::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:14::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:15::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:16::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:17::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:18::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:19::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:20::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:21::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:22::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:23::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:24::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:25::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:26::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:27::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:28::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:29::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:30::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:31::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:32::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:33::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:34::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:35::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:36::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:37::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:38::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:39::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:40::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:41::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:42::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:43::/64 onlink autoconfig
Aug  4 15:00:39.699: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:00:39.699: ICMPv6-ND:     prefix = 2001:DB8:44::/64 onlink autoconfig


and


Aug  4 15:03:57.027: ICMPv6-ND: Request to send RA for FE80::1EE6:C7FF:FE52:A6C0
Aug  4 15:03:57.027: ICMPv6-ND: Setup RA from FE80::1EE6:C7FF:FE52:A6C0 to FF02::1 on Vlan9
Aug  4 15:03:57.027: ICMPv6-ND:  MTU = 1500
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:1::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:2::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:3::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:4::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:5::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:6::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:7::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:8::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:9::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:10::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:11::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:12::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:13::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:14::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:15::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:16::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:17::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:18::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:19::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:20::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:21::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:22::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:23::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:24::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:25::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:26::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:27::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:28::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:29::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:30::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:31::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:32::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:33::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:34::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:35::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:36::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:37::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:38::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:39::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:40::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:41::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:42::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:43::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)
Aug  4 15:03:57.027: ICMPv6-ND:     prefix = 2001:DB8:44::/64 onlink autoconfig
Aug  4 15:03:57.027: ICMPv6-ND:          2592000/604800 (valid/preferred)

The software used on the cisco layer2 and layer3 switches.

software 6509-E = 15.1(2)SY2 adv-enterprise
software 2960S   =  15.2(1)E2

Interesting but the question that arose, " does any layer2 ipv6 enabled subnet need that many ipv6 prefixes ? " .  The answer is all up to you.


Ken Felix
NSE ( Network Security Expert) and Route/Switching Engineer.
kfelix  -----a----t---- socpuppets ---dot---com

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