Check bootp enabled router

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konigl Wed, 03/26/2003 - 05:12
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Do you mean (1) if the router is acting as a bootp or DHCP server? Or (2) if bootp or DHCP broadcasts received on one interface are being forwarded to a remote server on another interface?


Here's an answer to (2).


Look at the startup-config and running-config. If "ip helper-address" command is listed under a particular interface, then bootp broadcasts heard on that interface should be forwarded to the specified IP address.


The "ip helper-address" command forwards the following UDP ports by default:


time (37)

tacacs (49)

dns or domain (53)

bootp server or bootps (67)

bootp client or bootpc (68)

tftp (69)

netbios name service or netbios-ns (137)

netbios datagram service or netbios-dgm (138)


DHCP uses the same ports as bootp.


A sample configuration that supports forwarding only DHCP requests heard on two interfaces to a DHCP server (192.168.0.10) on a third interface follows. Note how forwarding (or blocking forwarding) of the other default protocols is done at the system level; while the helper-address is configured interface by interface.


interface ethernet0/0

description This is the subnet where the DHCP server lives

ip address 192.168.0.1 255.255.255.0

!

interface ethernet1/0

description This is where some DHCP clients live and need DHCP forwarded

ip address 192.168.1.1 255.255.255.0

ip helper-address 192.168.0.10

!

interface ethernet2/0

description This is where other DHCP clients live and need DHCP forwarded

ip address 192.168.2.1 255.255.255.0

ip helper-address 192.168.0.10

!

no ip forward-protocol udp time

no ip forward-protocol udp tacacs

no ip forward-protocol udp domain

no ip forward-protocol udp tftp

no ip forward-protocol udp netbios-ns

no ip forward-protocol udp netbios-dgm



Hope this helps.

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