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DHCP Relay agent on router in Packet tracer

Discussion in 'General Cisco Certifications' started by ahmadirad, May 23, 2012.

  1. ahmadirad

    ahmadirad New Member

    Dear all

    in packet tracer i have a router(R1) that have 4 FastEthernet port.

    Fa0/0: ------> SW1(Layer2) -----> PC1 (DHCP Client)
    Fa1/0: ------> SW2(L2) ---------> PC2 (DHCP Client)
    Fa8/0: ------> SW3(L2) ---------> PC3 (DHCP Client)
    Fa9/0: ------> SW4(L2) ---------> PC4 (DHCP Client)
    in subnet 4 (Fa9/0) i have a DHCP server and created 4 Scopes. pc4 get an ip address ( but another pcs cannot get ip from DHCP that is on Fa9/0 side. please some body help me to configure router to pass DHCP Request and get an ip address in its range.

    Best Wishes
  2. Simonvm

    Simonvm Kilobyte Poster

    You will have to configure DHCP relay on all the other interfaces, since DHCP uses only a Layer2 Broadcast.
    Using an IP HELPER you can tell your routers (or layer3 switches) to repackage that broadcast as a Layer 3 packet and send it to the DHCP server of your choice.

    The command, under all your interfaces that are in another subnet, is:

    ip helper-address <ip address of your dhcp-server>

    Cisco IOS IP Command Reference, Volume 1 of 4: Addressing and Services, Release 12.3 T - IP Addressing and Services Commands: idle through ip local-proxy-arp  [Cisco IOS Software Releases 12.3 T] - Cisco Systems
    Certifications: MCITP: EST, MCDST, MCTS, A+, N+, CCNP, CCNA Wireless
  3. ahmadirad

    ahmadirad New Member

    Thanks Simonvm,
    your solution resolved my problem.

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