In order for Branch-1 to forward a packet to Branch-2’s LANs, it has to send the packet out of its serial 0/0/1 interface. The exit interface is also considered the direction in which to reach these networks.
Using the exit interface displays the static route as being directly connected, hence the name Directly connected static route. Read the “L” on the slide. Explain how the link shows a 128 bit prefix and the “C” displays the actual prefix used. In this example, the subnet identified by the “C” is the 2001:DB8:A::2/127 and the address configured on the interface identified by the “L” or local host route is 2001:DB8:A::3/128
In this example, in order for Branch-1 to forward a packet to Branch-2’s LANs it must forward the packet to the next hop router in the direction of those networks. In this example, that would be the IPv6 address of Branch-2.
There is a noticeable difference how a directly connected and a recursive static route are displayed in the routing table. A directly connected static route shows that it is directly connected to an interface, while the recursive static route shows via the next hop router identified by its IPv6 address. In this example, in order for Branch-1 to route traffic to Brnach-2’s LANs, it will send it to the 2001:DB8:A::2 address which happens to be the IPv6 address configured on Branch-2. Now the router has to do a second routing table lookup to determine how to get to the 2001:DB8:A::2 network. Based on this information, the router will now forward the packet out of its serial 0/0/1 interface.
Fully specified static routes displays both the next hop router’s IPv6 address as well as the exit interface.
Fully specified static routes displays both the next hop router’s IPv6 address as well as the exit interface. As you can see in the routing table, a fully specified static route displays both the next hop router’s IPv6 address as well as the exit interface.
A default route is used when no other routes in the routing table match the packet destination IP address. In other words, when a more specific match does not exist. A default route is usually configured on a company's edge router that connects to the ISP’s network. The command for an IPv6 default route is ::/0. This is the IPv6 version of the all zero address (remember the :: is used to identify consecutive zeros) which is similar to the quad zero address used in an IPv4 default route. A default route can be configured as a directly connected, recursive, or as a fully specified static default route.
Notice how the default route is displayed in the routing table as an “S” because the correct name is a static default route but notice that the * (asterisk) is not used to identify a default route in an IPv6 routing table.
Notice how we can ping both LAN interfaces with only one static route entry in the routing table. Instead of configuring two static routes to reach Branch-2’s LANs, we can summarize them based on common bits in the network portion of the address. In this example, both addresses have the first 46-bits in common. 16 bits in the first two hextets and 14 bits in the 3rdhextet for a total of 63-bits. As you can see, we can ping each LAN interface with only one static route entry in the routing table.
Some of the output was omitted because it didn’t fit on the slide. 5 floating static routes were configured with an administrative distance of 91, one more that the routing protocol which in this case is EIGRP. The output to the left displays the IPv6 routing table with only the dynamic routes installed. When the primary path (interface s0/0/0) goes down, the dynamic routes are removed from the routing table and the floating static routes replace them. The Branch-1 will now route traffic to Branch-2 through the backup path (Serial 0/0/1).
IPv6 Static Routes
IPv6 Static Routes
Cisco Certified Instructor Trainer
Thomas A. Edison CTE HS
Network Architect, CCIE #36243
ABS Technology Architects