Ip Unnumbered Proof of Concept
As announced in the previous post, here is the proof of concept of the IP Unnumbered command.
I will use here exactly the same architecture as in the previous post :
Also, 2 conditions will be fulfilled here in order to proove IP Unnumbered works :
- no routing protocol anywhere, just static routing (via serial interfaces)
- no IP unnumbered command, but 2 different static IP addresses put on the S0/0 of each router :
- on R1 : 126.96.36.199
- on R2 : 188.8.131.52
- As you can see, random IP addresses have been taken, on completely different network, although on the same link.
Here is the configuration :
On R1 :
R1#sh run hostname R1 ! interface Ethernet0/0 ip address 184.108.40.206 255.0.0.0 half-duplex ! interface Serial1/0 ip address 220.127.116.11 255.255.255.0 serial restart-delay 0 clock rate 64000 ! ip route 10.0.0.0 255.0.0.0 Serial1/0 !
On R2 :
R2#sh run hostname R2 ! interface Ethernet0/0 ip address 10.0.0.1 255.0.0.0 half-duplex ! interface Serial1/0 ip address 18.104.22.168 255.0.0.0 serial restart-delay 0 clock rate 64000 ! ip route 22.214.171.124 255.0.0.0 Serial1/0 !
As you can see, there are static routes pointing to the other network, via the Interface and not the Next-Hop IP address, which is impossible on most of the non point-to-point link.
Here are the routing tables of R1 and R2 :
R1#sh ip route Gateway of last resort is not set S 10.0.0.0/8 is directly connected, Serial1/0 C 126.96.36.199/8 is directly connected, Ethernet0/0 C 188.8.131.52/24 is directly connected, Serial1/0 R2#sh ip route Gateway of last resort is not set C 10.0.0.0/8 is directly connected, Ethernet0/0 S 184.108.40.206/8 is directly connected, Serial1/0 C 220.127.116.11/8 is directly connected, Serial1/0
Now let’s test. I will use first a simple ping and a traceroute :
For the ping, on R1, note that I cannot use the default source IP address of the S0/0. Indeed, R2 wouldn’t know how to come back to this unknown IP address. I have to use an IP address of the network behind, for which R2 has a static route :
R1#ping Protocol [ip]: Target IP address: 10.0.0.1 Repeat count : Datagram size : Timeout in seconds : Extended commands [n]: y Source address or interface: 18.104.22.168 Type of service : Set DF bit in IP header? [no]: Validate reply data? [no]: Data pattern [0xABCD]: Loose, Strict, Record, Timestamp, Verbose[none]: Sweep range of sizes [n]: Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds: Packet sent with a source address of 22.214.171.124 !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 8/24/56 ms
Now a traceroute, same deal for the source IP address. See the first hop’s IP address ? It’s the one on R2 S0/0 :
R1#traceroute Protocol [ip]: Target IP address: 10.0.0.1 Source address: 126.96.36.199 Numeric display [n]: y Timeout in seconds : Probe count : Minimum Time to Live : Maximum Time to Live : Port Number : Loose, Strict, Record, Timestamp, Verbose[none]: Type escape sequence to abort. Tracing the route to 10.0.0.1 1 188.8.131.52 40 msec * 104 msec R1#
Aaaaand… IT WORKS !