December 2006
Intermediate to advanced
1188 pages
72h 8m
English
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Debugging DHCP
Problem
You want to debug a DHCP problem.
Solution
To debug the server events, use the following EXEC command:
Router1#debug ip dhcp server eventsThe following command will allow you to monitor the actual DHCP-related packets being transmitted and received by the router:
Router1#debug ip dhcp server packetDiscussion
The following debug capture shows a router performing normal housekeeping duties, such as updating its address pools, checking for expired leases, assigning new leases, and revoking expired leases:
Router1#debug ip dhcp server events
Sep 15 00:58:17.218: DHCPD: returned 172.25.1.51 to address pool COOKBOOK
Sep 15 00:58:22.566: DHCPD: assigned IP address 172.25.1.51 to client 0100.0103.85e9.87.
Sep 15 01:01:15.056: DHCPD: writing bindings to ftp://dhcp:bindsave@172.25.1.1/dhcp-leases-rtr1.
Sep 15 01:01:15.132: DHCPD: writing address 172.25.1.51.
Sep 15 01:01:15.148: DHCPD: wrote automatic bindings to ftp://dhcp:bindsave@172.25.1.1/dhcp-leases-rtr1.
Sep 15 01:01:58.816: DHCPD: checking for expired leases.
Sep 15 01:03:58.841: DHCPD: checking for expired leases.
Sep 15 01:05:58.859: DHCPD: checking for expired leases.
Sep 15 01:07:58.874: DHCPD: checking for expired leases.
Sep 15 01:09:58.885: DHCPD: checking for expired leases.
Sep 15 01:09:58.885: DHCPD: the lease for address 172.25.1.51 has expired.
Sep 15 01:09:58.885: DHCPD: returned 172.25.1.51 to address pool COOKBOOK.The next debug capture shows a typical DHCP client transaction between the client and router. ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.