A ping performed on the local IP address on a
multipoint Frame Relay interface does not work. This is because Frame Relay
multipoint physical and subinterfaces are non-broadcast. Recall that Ethernet
and point-to-point interfaces such as High-Level Data Link Control (HDLC) and
Frame Relay point-to-point sub-interfaces are broadcast. Because multipoint
interfaces can have multiple destinations, the router must have a mapping for
every destination. The router does not have any Layer 3 to Layer 2 mapping for
its own address and does not know how to encapsulate the packet. An
encapsulation failure results.
Furthermore, ping is unsuccessful from one spoke to
another in a hub and spoke configuration. This is because there is no mapping
for the local IP address, and none were learned by way of Inverse ARP. But if a
static map is configured with the frame-relay map command for the local IP
address or one for the remote spoke to use the local DLCI,
ping will be successful.
Before adding the static Frame-Relay map, the result of pinging a local
interface will be as follows:
Router#ping
3.1.3.3
Type escape sequence to
abort.
Sending 5, 100-byte ICMP Echos to 3.1.3.3, timeout is 2
seconds:
.....
Success rate is 0 percent
(0/5)
To permit the pinging of local Frame-Relay
interfaces, the following static map command must be added:
Router#configure terminal
Enter configuration commands, one per line. End with
CNTL/Z.
Router(config)#interface serial
0/1
Router (config-if)#frame-relay map ip 3.1.3.3
160
This can be verified using the show frame-relay
map command:
Router#show frame-relay
map
Serial0/1 (up): ip 3.1.3.1 dlci 180(0xA0,0x2800),
dynamic, broadcast, status defined, active
Serial0/1 (up): ip
3.1.3.2 dlci 160(0xA0,0x2800), static, CISCO, status defined,
active
Serial0/1 (up): ip 3.1.3.3 dlci 160(0xA0,0x2800),
static, CISCO, status defined, active
It will now be
possible to ping the local interface:
Router#ping
3.1.3.3
Type escape sequence to
abort.
Sending 5, 100-byte ICMP Echos to
3.1.3.3, timeout is 2 seconds: !!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max =
64/68/76 ms
The running configuration file for Serial 0/1
is reproduced below:
interface
Serial0/1
ip address 3.1.3.3 255.255.255.0
no
ip directed-broadcast
encapsulation
frame-relay
frame-relay map ip 3.1.3.2
160
frame-relay map ip 3.1.3.3
160
frame-relay interface-dlci
160
!