vlans

[billyj1900]

I have DHCP running on R1 and can receive DHCP on host1 off of SW1. R1 is has a serial connection to R2. I am running EIGRP 1 on both routers. I have advertised all of my DHCP addresses and management address on R1. I have advertised my management address on R2 and I can see my vlan IP addresses in my routing table on R2. I have an IP route statement on R1 0.0.0.0 0.0.0.0 10.1.155.2 (R2 s0/0). I also have an IP route on R2 of 0.0.0.0 0.0.0.0 10.1.155.1 (R1 s0/0). I have a SW5 connected to R2 and host5 connected to that switch. Why can't I receive DHCP from R1 on host5? I can ping the DHCP addresses from my host5 if I give it a management address.

 

[dearingkr]

DHCP Request is a broadcast.
By default broadcasts are not routed.

However, you can forward DHCP broadcasts by configuring a DHCP Relay in your router on that VLAN.

In your case, assuming R2 is not handling DHCP:

int f0                          <=R2 LAN interface
ip helper-address 192.168.1.1   <=IP address on R1 LAN interface
exit

Note: these are Cisco commands.


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[billyj1900]

I tried that I still didn't get a DHCP address.

 

[dearingkr]

Is host5 on the same VLAN (subnet) as R2 LAN interface?

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[billyj1900]

host5 has switchport access vlan 2 on it port connected to SW5. SW5 is on the same subnet as R2 fa0/1

 

[dearingkr]

Just to clarify...
R2 fa0/1 IP address: is in VLAN2's subnet?

Is the connection between R2 & SW5 trunked (multiple VLANs)?


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[billyj1900]

Yeah the port to sw5 and R2 is trunked.

 

[dearingkr]

The DHCP server is going to use whatever scope corresponds to the IP address of the DHCP Relay.

For example:
If R2 fa0/1 IP address is 10.1.1.1 and DHCP relay is configured on that interface
Then R1 DHCP server will use a scope that matches 10.1.1.0 subnet.

If you have multiple VLANs on that interface, you need to configure separate IP addresses on the VLANs

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