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562 Chapter 8: WAN Protocols and Design
The show frame-relay map command provides a full insight into mapping. The neighboring
routers' IP and IPX addresses correlate to the DLCIs. This is possible because the Inverse ARP
messages flow over a VC; the Inverse ARP contains a Layer 3 protocol type and address. The
DLCI correlates to a subinterface based on configuration.
The messages about Inverse ARP in the debug frame-relay events output is not so obvious.
One easy exercise is to search for the hex version of the IP and IPX addresses in the output.
These addresses have been highlighted in Example 8-19. For example, the first 3 bytes of
140.1.1.0 are 8C 01 01 in hexadecimal; this field happens to start on the left side of the output,
so it is easy to recognize visually. The IPX address should be much easier to recognize because
it is already in hexadecimal format in the configuration.
RouterC(config-subif)#no shutdown
RouterC(config-subif)#^Z
RouterC#
Serial0.1: FR ARP input
Serial0.1: FR ARP input
Serial0.1: FR ARP input
datagramstart = 0xE42E58, datagramsize = 30
FR encap = 0x7C510300
80 00 00 00 08 06 00 0F 08 00 02 04 00 09 00 00
8C 01 01 01 7C 51 8C 01 01 03
datagramstart = 0xE427A0, datagramsize = 46
FR encap = 0x7C510300
80 00 00 00 08 06 00 0F 81 37 02 0A 00 09 00 00
00 00 00 01 02 00 AA AA AA AA 7C 51 00 00 00 01
02 00 CC CC CC CC 1B 99 D0 CC
datagramstart = 0xE420E8, datagramsize = 30
FR encap = 0x7C610300
80 00 00 00 08 06 00 0F 08 00 02 04 00 09 00 00
8C 01 01 02 7C 61 8C 01 01 03
Serial0.1: FR ARP input
datagramstart = 0xE47188, datagramsize = 46
FR encap = 0x7C610300
80 00 00 00 08 06 00 0F 81 37 02 0A 00 09 00 00
00 00 00 01 02 00 BB BB BB BB 7C 61 00 00 00 01
02 00 CC CC CC CC 1B 99 D0 CC
Example 8-19
Frame Relay Maps and Inverse ARP on Router C (Continued)
ch08.fm Page 562 Monday, March 20, 2000 5:17 PM