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jtiesi's avatar
jtiesi
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Jul 19, 2021

M4100-50G - How to pass DHCP from another M4100-50G

Hello Community,

 

I'm using two M4100-50G switches to bring internet to a remote transmitter site using a Studio to Transmitter link (I work in broadcast engineering/IT).  I have successfully configured one of the M4100-50G switches to pass DHCP data through one vlan.  On the other end of the STL is a second M4100-50G, slightly newer than the one I've already successfully configured to pass DHCP data.  However, the 2nd switch isn't passing DHCP and I can't figure out why.  I have looked at all the settings that I remember changing on the M4100 that is working and duplicated it on the other one but its not working.  So, my question is where do I start looking?  My vlan names match.  Other vlans running through both switches work fine so I know the connection is fine.  On the vlan that needs DHCP, all the ports that are part of that vlan are untagged.  DHCP snooping is off.  I have not enabled DHCP L2 relay nor do I have any L3 routing enabled.  In my understanding, if the ports between the switches are configured as Access ports then I shouldn't have any trouble.

 

Let me also mention that I see the DHCP at the other end of the STL if I bypass the managed switch so I know the problem is with the switch.  I just can't quite figure out where.

 

Any help you can give is appreciated and will be noted in my notes at the T.V. station I work at.

1 Reply

  • Read like the VLAN config for the VLAN you use as an untagged VLAN (note: The VAN name is not relevant - it's just documenttion). This [U]ntag happes at the port or LAG level, similar the PVID setting does define the (typically same) VLAN where untagged ingress frames on the port are associated to.

     

    Similar, the link or links making up the connection between the switches must be configured to carry this VLAN where you need DHCP. Either keep it as the one and only untaged one (same PVID again), or make it [T]aged at both ends of the switch interconnect links, typically named trunks.

     

    Passing DHCP/BOOTP on a flat network is straight forward layer 2.