Core Switch 6500 - DHCP

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Oct 26th, 2007
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I have issue with my network.

Actuallty I have 6500 Switch with Firewall Moduler. and connected to DHCP Server <Mirosoft Version>. And the VLAN 10. is behind the firewall and from there connected to DHCP Server. WHen the user try to get IP address from DHCP they con't. But when we change the vlan 109 its working fine. After I allowed in firewall all the traffic for the server. DHCP can sea the request but cant provide IP address.

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royalblues Fri, 10/26/2007 - 23:40
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What is the Gateway for the VLAN, the FWSM or the MSFC and where is the DHCP located

If it is the FWSM, then you would need to allow udp port 67 & 68 from any source (remember DHCP request soruce address is

Also if the DHCP is on a seperate segment, you need to configure a DHCP relay agent with the help of ip helper-address



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b.fawaz.emr Fri, 10/26/2007 - 23:50
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Thank you For replay

The connectivity like:

Core_SW_6500 + Firewall Module--->Dump Switch--->DHCP Server

- And the port 67&68 from any source is enabled.

- The DHCP IP helper address configured.

- The DG for VLAN is the CORE.

THe last thing found the VLAN10 its routed to Firewall for the DHCP connected to VLAN10 the DHCP can sea the request but not give IP address. But when we configure new vlan109 and is direct to DHCP without routed to firewall working fine.

royalblues Sat, 10/27/2007 - 00:00
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In this case, th switch would send a unicast DHCP message with the VLAN IP address as the source towards the DHCP server.

Make sure you have allowed the traffic both ways from the SVI towards the DHCP and the DHCP server towards the SVI adddress.




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