about earlier? They advertised R1 as a router, and IPv6 used that information. If we look at show ipv6 interface fo/1 on R4 before and after I added the ipv6 unicast-routing command on R1, we see an inter- esting difference: Before: R4#sho ipv6 int fo/1 FastEtherneto/1 is up, line protocol is up IPv6 is enabled, link-local address is FE80::212:80FF:FE31:E2 Global unicast address(es): AAAA : AAAA: AAAA 101::4, subnet is AAAA:AAAA:AAAA:101::/64 Joined group address (es): FF02: :1 FF02: FF02 :1: FF00: FF02 : 1: FF31 : E259 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds After: R4#sho ipv6 int fo/1 FastEtherneto/1 is up, line protocol is up IPv6 is enabled, link-local address is FE80::212:80FF:FE31:E259 Global unicast address(es): AAAA: : AAAA: AAAA: 101::4, subnet is AAAA:AAAA:AAAA:101::/64 Joined group address (es): FF02 :1 FF02 :2 FF02: :1:FF00:4 FF02 1: FF31 E259 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ND DAD is enabled, number of DAD attempts: 1 Simple Router Configuration ND reachable time is 30000 milliseconds Default router is FE80::212:43FF:FEB9:2C71 on FastEtherneto/1 The interface now shows a default router with the EUI-64 IPv6 address of R1's F0/1 interface. Want to bet there's a similar default router shown on the f0/0 interface of R6? Let's take a look: R6#sho ipv6 int fo/o FastEtherneto/o is up, line protocol is up IPv6 is enabled, link-local address is FE80::214:6AFF:FEA2:D438 Global unicast address (es) AAAA: AAAA: AAAA: 1::6, subnet is AAAA:AAAA:AAAA:1::/64 AAAA AAAA AAAA 1:214: 6AFF:FEA2:D438, subnet is AAAA:AAAA:AAAA:1::/64 [PRE] valid lifetime 2591990 preferred lifetime 604790 Joined group address (es) : FF02:: FF02: FF02 : :1: FF00 6 FF02 : : 1: FFA2 : D438 MTU is 1500 bytes ICMP error messages limited to one every 100 milliseconds ICMP redirects are enabled ND DAD is enabled, number of DAD attem