242 PART II Core Protocols admin@CE6# set unit 0 tunnel destination 10.10.11.1; /*destination address on LAN1 interface*/ admin@CE6# set unit 0 family inet6 address fc00:ffb3::/32 /*LAN1 addresses*/ [edit interfaces gr-1/0/0] admin@CE0# set interfaces gr-1/0/0 admin@CE0# set unit 0 tunnel /*source address on LAN1 admin@CE0# set unit 0 tunnel /*destination address on admin@CE0# set unit 0 family /*LAN2 addresses*/ source 10.10.11.1; interface*/ destination 10.10.12.1; LAN2 interface*/ inet6 address fc00:ffb3::/32 Now we should be able to ping and traceroute an IPv6 address on LAN1 (in this case, fc00:ffb3:d5:a:20e:cff:fe3b:8f95 for bsdclient ) from the customer-edge router on LAN2. And we can. Note that, because of the tunnel, the destination seems to be only two hops away. admin@CE6> ping inet6 count 4 source fc00:fe67:d4:b:205:85ff:fe8b:bcdb fc00:ffb3:d5:a:20e:cff:fe3b:8f95 PING6(56=40+8+8 bytes) fc00:fe67:d4:b:205:85ff:fe8b:bcdb --> fc00:ffb3:d5:a:20e:cff:fe3b:8f95 16 bytes from fc00:fe67:d4:b:205:85ff:fe8b:bcdb, icmp_seq=0 time=0.900 ms 16 bytes from fc00:fe67:d4:b:205:85ff:fe8b:bcdb, icmp_seq=1 time=0.728 ms 16 bytes from fc00:fe67:d4:b:205:85ff:fe8b:bcdb, icmp_seq=2 time=0.856 ms 16 bytes from fc00:fe67:d4:b:205:85ff:fe8b:bcdb, icmp_seq=3 time=0.838 ms hlim=64 hlim=64 hlim=64 hlim=64 admin@CE6> traceroute inet6 source fc00:fe67:d4:b:205:85ff:fe8b:bcdb fc00:ffb3:d5:a:20e:cff:fe3b:8f95 traceroute6 to fc00:ffb3:d5:a:20e:cff:fe3b:8f95 (fc00:ffb3:d5:a:205:85ff: fe88:ccdb) from fc00:fe67:d4:b:205:85ff:fe8b:bcdb, 30 hops max, 12 byte packets 1 fc00:ffb3:d4:b:205:85ff:fe88:ccdb (fc00:ffb3:d4:b:205:85ff:fe88:ccdb) 1.059 ms 0.979 ms 0.819 ms 2 fc00:ffb3:d5:a:20e:cff:fe3b:8f95 (fc00:ffb3:d5:a:20e:cff:fe3b:8f95) 0.832 ms 0.887 ms 0.823 ms Let's take a look at the some basic types of router architectures that can be used to implement these packet-forwarding strategies. ROUTER ARCHITECTURES There are three main steps that a router must follow to process and forward a packet to the next hop. Processing a packet means to check an incoming packet for errors and other parameters, looking up the destination address in a forwarding table to