SGE2010 - Relaying traffic and setting up DHCP

[ravn]

Hei

We just purchased a SGE2010 switch which we want to use to replace the switches in our office panel. So far i have gained access to the switch and assigned it a static ip.adress on our net, but i can't get it to relay traffic from our entrypoint switch. I have a test machine which is set up with a static ip as well and testet the connection ok, but as soon as i set the switch in between the traffic isn't relayed.

The whole idea was to use this switch as a dhcp server as well. But i thought it would be a start to at least get the traffic relayed before i started the dhcp part.

The only configuration adjustments i have done from factory settings are the following: (note that ip's are slightly adjusted, but consistant for privacy reasons)

IP4 configuration

1. Assigned a static ip: 95.59.69.148
2. Assigned a submask: 255.255.255.192
3. Assigned a user defined gateway: 95.59.69.129

Dns configuration

1. Assigned a dns adress ip: 95.59.0.100 as active
2. Assigned a dns adress ip: 95.59.0.200

All these settings are the typical settings we use when we assign a server with a static ip so it doesn't pick one up from our excisting dhcp server. So my main question is why on earth isn't it relaying the traffic ?

In addition we are interested in killing the old dhcp server (with stones i hope) and setting up dhcp on the sge2010. The current dhcp is a OS.X (yes a mac) dhcp server with the following setup:

• Subnet (for dynamic ip's)
  Starting ip: 95.59.69.179
  Ending ip: 95.59.69.190
  Subnet: 255.255.255.192
  
  
• Router ip: 95.59.69.129
  Lease time: 3 hours
  
  
• The range 95.59.69.130 to 95.59.69.149 we setup manually on servers, hardware etc.
  
  
• DNS Server: 95.59.0.100 & 95.59.0.200
  Default search domain: no-dns-available.example.com
  
  
• And then we have a group of static mappings on Mac-adresses
  from ip: 95.59.69.150
  to ip: 95.59.69.178

I tried to see in the setup where i could spesify static mappings range etc, but i can't say it got me anywhere. So my second question is how would i setup a mathing dhcp server as the one descriped above ?

It's nice to finally convince the ceo's to move the dhcp to a better metal, but it's not as nice having a hard time setting it up. I would apprecitate every possible leeds and sugestions since i'm pretty much stuck.

With thanks in advance

Rafn.R

[David Hornstein · Accepted solution]

Hi

My SGE2000P is relaying DHCP requests to my DHCP server.

I used my default VLAN1 as a routed interface to unicast the DHCP relay request to my DHCP server (UC520 ISR router) that resides on that VLAN 1.

My Vlan 1 interface on my SGE2000P  has a IP address of 192.168.10.254.

My gateway address for the potential IP hosts on VLAN 2 will be THE IP ADDRESS I HAVE ASSIGNED TO VLAN 2, because the PC's or IP hosts attached to VLAN2 will use the VLAN2 IP interface as their gateway. That's just how it works!!

PC hosts on VLAN 2 need a default route out and they use the IP address I assigned to VLAN2 as their next hop to get out of VLAN2 to the real world .

That address can be seen below.

DHCP relay is enabled with option 82

I have selected VLAN2 as a VLAN interface as seen below;

I have two untagged ports in VLAN2, and I attached a IP host to G1 so that I could test the DHCP relay.

I am getting the following debugging  output from my dhcp server, so i know the relay is working.

002624: Dec  5 19:40:08.575: DHCPD: checking for expired leases.

002625: Dec  5 19:40:58.408: DHCPD: Sending notification of DISCOVER:

002626: Dec  5 19:40:58.408:   DHCPD: htype 1 chaddr 0025.84d8.d008

002627: Dec  5 19:40:58.408:   DHCPD: remote id 020a0000c0a80a0101080001

002628: Dec  5 19:40:58.408:   DHCPD: circuit id 00000000

002629: Dec  5 19:40:58.408: DHCPD: Seeing if there is an internally specified pool class:

But gotta admit I have opened a case on this with the small Business Support Center, as I  believe I can see something wrong on my DHCP server debug.

But the bottom line is I am seeing the  WAN router/DHCP server seeing the DHCP request coming in.

The only way the broadcast DHCP requests can get to DHCP server  is if the SGE2000P switch is taking those broadcast  DHCP requests and unicasting them or relaying them to my DHCP server at IP address 192.168.10.1.

So in other words DHCP relay is working.

I would ask you to please  check the SGE2010 Administrators guide as it clearly shows how to configure DHCP relay on the SGE2010.

Even thought the Screen capture shows and older version of code below.  I did update my SGE2000P tonight to the currently Generally Available (GA) version of code.

Just outa interest , if you were to telnet to the switch, is your switch is layer 2 or layer 3 mode.

I can also tell from your screen capture that your uplink ports are in stacking mode.

Maybe if you are not using stacking, you can set your switch to layer 3 mode and standalone mode

regards Dave

[ravn]

Hi David

Thank for a very detailed and informative reply.

I started by telnetting to the switch and changed the mode from layer 2 to layer 3 and the configuration from stackable to standalone.

After that i configured the ip again and after that the switch routed the traffic

It even routed the traffic with the options "DHCP Relay: Disable" & "Option 82: Disable" are there any pros and cons on having these settings enabled ?

The interesting part was that the switch automaticly picked up the static routing, so that i didn't even have to configure. Since the traffic was now routing i added the dns configuration and then i though i could try to setup the switch as an DHCP Server.

I just want to ask you just to be sure. Is it possible to setup the switch as a dhcp server ? Or are all the configuration alternatives related to relaying and using an excisting dhcp server ?

After i confirmed that the switch was relaying traffic i disconneted it from the network and tried setting up the switch as an dhcp server. Tried different scenarios but i couldn't get it to assign an ip to a connected device. Is it possible and how ? Slightly related to my previous question.

Below you'll find screens from my current setup and as i mentioned above it now a standalone in layer 3.

Thank you again for the help so far.

Regard

Rafn.R

[David Hornstein]

Hi Rafn,

I wish i could say something positive for you.

The switch doesn't have  a DHCP server built in.

The switch is designed to forward DHCP requests, via DHCP relay to something like a Linix/unix/BSD  DHCP server or a Cisco Router that can handle IP allocation to multiple DHCP scopes.

If the SGE2010 itself does receive a IP address via DHCP it should also receive a default route, hence you noticed it had a default route.

The switch will switch at Layer 3 between VLANs, but still requires that IP hosts have either;

1. Static IP addresses or

2. the VLANs connected to seperate DHCP servers or;

3. use DHCP relay to use option 82 it identify the circuit ID ( vlan ) from where the DHCP request is coming from, then it will allocate a IP address.

The example below shows part of a a linux DHCP conf file  where it checks the circuit ID field for a particular VLAN ID, in the case below VLAN ID=2.

[ravn]

Hi again

Well that was a downfall. The most important thing is that the traffic relaying is working. Guess i have to find another solution for the dhcp. What would you recomend ? My thought was just to get the dhcp server away from a standard server machine and over to a deticated metal. I have a entry point switch which i could perhaps switch out with another one which has dhcp, for a cisco or a ZyXEL. The one i have to day is a ZyXEL ES-2108G

http://www.zyxel.com/web/product_family_detail.php?PC1indexflag=20040520161143&display=6857&CategoryGroupNo=B0AB459F-0530-404E-BDC1-A8FFC6193DC9

Note that i am using the fiber port for incoming traffic.

It would be nice to have a dhcp server on a switch with administrative gui. Thats what i was hoping when i bought the sge2010, it would make it easier assigning static ip's to mac adresses etc.