The HA R1 is advertising (“redistribute mobile”) reachability to the mobile network 140.80.1.0/24 (on the MR R3) to the internet, thereby attracting packets that are destined for this subnet. MR R3 will keep the same IP address 150.1.1.1 while roaming between its home network 150.1.1.0/24 and foreign networks 200.2.2.0/24, 200.6.6.0/24. So When MR R3 is in foreign network 200.2.2.0/24, it will acquire a care-of address 2.2.2.2 from the FA R2. After receiving the care-of address, the MR R3 will register this address with its HA R1. The HA R1 will create a mobility binding table that maps the home IP address 150.1.1.1 of the MR R3 to the current care-of address 2.2.2.2 of the MR R3.
Now when any device on the Internet, called a corresponding node (CN), sends a packet to the mobile network (more specifically to 140.80.1.1), the packet is routed to the HA R1. Then the HA R1 will double tunnel it (outer tunnel to FA R2 care-of address 2.2.2.2 and inner tunnel to MR R3 itself). The FA R2 removes the outer tunnel header and delivers the inner tunneled packet to the connected MR R3. MR R3 performs another decapsulation to deliver the packet to the destination node 140.80.1.1 on the mobile network.
However, packets sent from the mobile network 140.80.1.0/24 are routed directly to the CN unless a reverse tunnel is configured.
We will do some testing and verification when mobile router R3 is in the foreign network 200.2.2.0/24 on R2.
Rack1R1#show ip route | inc ^M
M 140.80.1.0 [3/1] via 0.0.0.0, 00:15:18, Tunnel0
M 150.1.1.1/32 [3/1] via 2.2.2.2, 00:15:18, Tunnel1
Rack1R1#show ip mobile binding
Mobility Binding List:
Total 1
150.1.1.1:
Care-of Addr 2.2.2.2, Src Addr 2.2.2.2
Lifetime granted 00:01:00 (60), remaining 00:00:55
Flags sbdmg-t-, Identification CE22A5D5.F4C99770
Tunnel1 src 1.1.1.1 dest 2.2.2.2 reverse-allowed
MR Tunnel0 src 1.1.1.1 dest 150.1.1.1 reverse-allowed
Routing Options -
Mobile Networks: 140.80.1.0/255.255.255.0 (S)
Rack1R1#sh ip mobile tunnel
Mobile Tunnels:
Total mobile ip tunnels 0
Tunnel0:
src 1.1.1.1, dest 2.2.2.2
encap IP/IP, mode reverse-allowed, tunnel-users 1
Input ACL users 0, Output ACL users 0
IP MTU 1480 bytes
Path MTU Discovery, mtu: 0, ager: 10 mins, expires: never
outbound interface FastEthernet0/1
HA created, fast switching enabled, ICMP unreachable enabled
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 drops
20 packets output, 23125 bytes
Tunnel1:
src 1.1.1.1, dest 150.1.1.1
encap IP/IP, mode reverse-allowed, tunnel-users 1
Input ACL users 0, Output ACL users 0
IP MTU 1460 bytes
Path MTU Discovery, mtu: 0, ager: 10 mins, expires: never
outbound interface Tunnel0
HA created, fast switching enabled, ICMP unreachable enabled
Mobile Tunnels:
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 drops
20 packets output, 22725 bytes
Rack1R1#show ip mobile mobile-networks
Mobile Networks:
MR 150.1.1.1 [network behind the mobile router]:
Configured: 140.80.1.0/255.255.255.0
Registered:
Rack1R2#sh ip route | be Gateway
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
O 1.1.1.0 [110/3] via 180.1.27.7, 15:28:38, FastEthernet0/1
O 222.22.2.0/24 [110/2] via 180.1.27.7, 15:28:48, FastEthernet0/1
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, Loopback0
O 200.6.6.0/24 [110/3] via 180.1.27.7, 15:28:48, FastEthernet0/1
140.80.0.0/24 is subnetted, 1 subnets
O E2 140.80.1.0 [110/20] via 180.1.27.7, 00:29:32, FastEthernet0/1
6.0.0.0/24 is subnetted, 1 subnets
O 6.6.6.0 [110/3] via 180.1.27.7, 15:28:48, FastEthernet0/1
C 200.2.2.0/24 is directly connected, FastEthernet0/0
180.1.0.0/24 is subnetted, 3 subnets
O 180.1.17.0 [110/2] via 180.1.27.7, 15:28:48, FastEthernet0/1
C 180.1.27.0 is directly connected, FastEthernet0/1
O 180.1.67.0 [110/2] via 180.1.27.7, 15:28:48, FastEthernet0/1
150.1.0.0/16 is variably subnetted, 2 subnets, 2 masks
O 150.1.1.0/24 [110/3] via 180.1.27.7, 00:29:32, FastEthernet0/1
M 150.1.1.1/32 [3/1] via 150.1.1.1, 00:30:09, FastEthernet0/0
[3/1] via 150.1.1.1, 00:00:08, FastEthernet0/0
Rack1R2#sh ip mobile tunnel
Mobile Tunnels:
Total mobile ip tunnels 0
Tunnel0:
src 2.2.2.2, dest 1.1.1.1
encap IP/IP, mode reverse-allowed, tunnel-users 1
Input ACL users 0, Output ACL users 0
IP MTU 1480 bytes
Path MTU Discovery, mtu: 0, ager: 10 mins, expires: never
outbound interface FastEthernet0/1
FA created, fast switching enabled, ICMP unreachable enabled
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
20 packets input, 23125 bytes, 0 drops
0 packets output, 0 bytes
Rack1R2#show ip mobile globals
IP Mobility global information:
Home Agent is not enabled
Foreign Agent
Pending registrations expire after 7 secs
Care-of addresses advertised
Mobile network route injection disabled
Loopback0 (2.2.2.2) - up
1 interface providing service
Encapsulations supported: IPIP and GRE
Tunnel fast switching enabled, cef switching enabled
Tunnel path MTU discovery aged out after 10 min
NAT UDP Tunneling support enabled
UDP Tunnel Keepalive 110
Forced UDP Tunneling disabled
Rack1R2#show ip mobile visitor
Mobile Visitor List:
Total 1
150.1.1.1:
Interface FastEthernet0/0, MAC addr 0006.533a.2581
IP src 150.1.1.1, dest 200.2.2.254, UDP src port 434
HA addr 1.1.1.1, Identification CE22AC48.A0CA5400
Lifetime 00:01:00 (60) Remaining 00:00:32
Tunnel0 src 2.2.2.2, dest 1.1.1.1, reverse-allowed
Routing Options -
Rack1R2#show ip mobile interface
IP Mobility interface information:
Interface FastEthernet0/0:
IRDP (includes agent advertisement) enabled
Prefix Length not advertised
Lifetime is 60 seconds
Foreign Agent service provided
Foreign Agent challenge disabled
Reverse tunnel not supported
No registration required
Not busy
Home Agent access list:
Registration revocation disabled
Current number of visitors: 1
Rack1R3#sh ip route | be Gateway
Gateway of last resort is 200.2.2.254 to network 0.0.0.0
1.0.0.0/32 is subnetted, 1 subnets
M 1.1.1.1 [3/1] via 200.2.2.254, 00:50:11, Ethernet0/0
140.80.0.0/24 is subnetted, 1 subnets
C 140.80.1.0 is directly connected, Loopback0
200.2.2.0/32 is subnetted, 1 subnets
M 200.2.2.254 [3/1] via 200.2.2.254, 00:50:11, Ethernet0/0
150.1.0.0/24 is subnetted, 1 subnets
C 150.1.1.0 is directly connected, Ethernet0/0
M* 0.0.0.0/0 [3/1] via 200.2.2.254, 00:50:11, Ethernet0/0
Rack1R3#sh ip mobile tunnel
Mobile Tunnels:
Total mobile ip tunnels 1
Tunnel0:
src 150.1.1.1, dest 1.1.1.1
encap IP/IP, mode reverse-allowed, tunnel-users 1
IP MTU 1480 bytes
Path MTU Discovery, mtu: 0, ager: 10 mins, expires: never
outbound interface Ethernet0/0
MR created, fast switching enabled, ICMP unreachable enabled
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
20 packets input, 22725 bytes, 0 drops
0 packets output, 0 bytes
Rack1R3#show ip mobile router
Mobile Router
Enabled 08/03/09 21:04:42
Last redundancy state transition NEVER
Configuration:
Home Address 150.1.1.1 Mask 255.255.255.0
Home Agent 1.1.1.1 Priority 100 (best) (current)
Registration lifetime 65534 sec
Retransmit Init 1000, Max 5000 msec, Limit 3
Extend Expire 120, Retry 3, Interval 10
Monitor:
Status -Registered-
Active foreign agent 200.2.2.254, Care-of 2.2.2.2
On interface Ethernet0/0
Tunnel0 mode IP/IP
Rack1R6#ping 140.80.1.1 size 1460 df-bit
Type escape sequence to abort.
Sending 5, 1460-byte ICMP Echos to 140.80.1.1, timeout is 2 seconds:
Packet sent with the DF bit set
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/8 ms
Rack1R6#ping 140.80.1.1 size 1461 df-bit
Type escape sequence to abort.
Sending 5, 1461-byte ICMP Echos to 140.80.1.1, timeout is 2 seconds:
Packet sent with the DF bit set
M.M.M
Success rate is 0 percent (0/5)
Rack1R6#trace 140.80.1.1
Type escape sequence to abort.
Tracing the route to 140.80.1.1
1 180.1.67.7 4 msec 4 msec 0 msec
2 180.1.17.1 4 msec 0 msec 0 msec
3 150.1.1.1 4 msec * 0 msec