Wednesday, December 17, 2008

not much to talk with the ip helper address command .. you can foreward specified ports and also mention whether tcp / udp as configuring ip helper-address will not only query for dhcp but also ton of other services you can redirect , open or reserver a port with protocol forwarding feature

CODE
r1#config t
Enter configuration commands, one per line. End with CNTL/Z.
r1(config)#int loopback1
r1(config-if)#ip helper-address ?
A.B.C.D IP destination address
global Helper-address is global
vrf VRF name for helper-address (if different from interface VRF)

r1(config-if)#ip helper-address 172.16.2.1
r1(config-if)#end
r1#show ip
*Mar 1 01:21:16.907: %SYS-5-CONFIG_I: Configured from console by console
r1#show ip help
r1#show ip helper-address
Interface Helper-Address VPN VRG Name VRG State
Loopback1 172.16.2.1 0 None Unknown
r1#config t
Enter configuration commands, one per line. End with CNTL/Z.
r1(config)#ip for
r1(config)#ip forward-protocol ?
nd Sun's Network Disk protocol
sdns Network Security Protocol
spanning-tree Use transparent bridging to flood UDP broadcasts
turbo-flood Fast flooding of UDP broadcasts
udp Packets to a specific UDP port

r1(config)#ip forward-protocol udp 50000
r1(config)#end


and for example as mentioned if you wanted to foreward any other service you search for protocol port number and find it and forward it

CODE
r1#show ip port-map | i smtp
Default mapping: smtp tcp port 25 system defined

r1#show ip port-map | i bittor
Default mapping: bittorrent tcp port 6881...6884 system defined
Default mapping: bittorrent tcp port 6885...6888 system defined
Default mapping: bittorrent tcp port 6889 system defined
r1#


these are some of the details covering the dhcp services ... next on to ipv6

guday

by MY CCIE JOURNEY

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