SG300/500 InterVLAN Routing Issue + DHCP Relay

[tomislavtomasic]

I would like to communicate between VLAN's on my switch configuration.

I would also like to enable clients to be assigned different DHCP scopes based on VLAN membership.

Layer 3 mode is enabled on all switches.

SG-500 is the central point to witch 5 SG-300 switches are connected.

On 5 SG-300 switches I have configured 5 separate VLANs - VLAN2 [192.168.1.0/24], VLAN3 [172.16.3.0/24], VLAN4 [172.16.4.0/24], VLAN5 [172.16.5.0/24],VLAN6 [172.16.6.0/24.]

On SG-500 I have configured all 5 VLANs from SG-300 switches.

I need to have 172.16.x.0/24 clients being able to receive DHCP configuration from a DHCP server (192.168.1.8) located on 192.168.1.0/24 subnet.

I have enabled DHCP relay on SG-500 interfaces recieving VLAN3..5 subnets traffic.

When I issue a DHCP request from a client on VLAN3..5 subnets I do not receive a DHCP configuration response.

When I set up a static IP on a client from VLAN3..5 subnets, I cannot ping VLAN2 IP addresses.

What works is, setting an IP address on default VLAN1, but I do not want any existing or future added switch to be able to automatically receive IP configuration across networks by using VLAN1.

Why can't I ping from VLAN3..5 to VLAN2?

Do I need to set-up static routes on SG-500 to enable inter-vlan routing or will it handle directly connected VLAN routing itself?

How do I set-up DHCP relay for VLAN3..5 clients?

Any suggestions on how to get this working?

Thanks,

Tomislav

[Anup Sasikumar]

Hi Tomislav,

I don't have much expertise in SMB Switches but based on the details you have provided , intervlan communication doesn't seem to be happening.

1 - Are you able to ping to Interface VLAN2/3/4/5/6  on SG500 Switch from machines connected to corresponding VLANs on SG300 Switches ?

2 - Is the default gateway on the machines set to corresponding interface VLAN IPs ?

Regards,
Anup

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[tomislavtomasic]

Hi Anup,

1 - I cannot ping to VLAN interfaces on SG500 switches.

2 - Yes, I set the default GW to interface VLAN IPs.

Best,

Tomislav

[Anup Sasikumar]

Hi Tomislav,

For InterVLAN communication to happen there should defintely be connectivity to corresponsing SVIs or interface VLANs configured on the SG500 from nodes in VLANs on SG300. I guess it can be due to the following reasons

1. If there are multiple VLANs in each SG300 and the connection from SG300 to SG500 is not confiured as a trunk link and is passing only a particular VLAN traffic. Are they trunk links (with ports configured as trunk ports on both ends ) with the correct encapsulation?

2. If they are trunk links, is the VLAN traffic being blocked due to pruning or something on the trunk links ?

Basically I think the root cause is that the traffic from the VLAN is not reaching your SG500 interface VLAN and that needs to be sorted out first.

I am just a novice but I had a seriously messed up VLAN situation (which was resolved eventually ! Hoo !  ) and that sure helped me much in understanding VLANs better.

That was not with SMB Switches anyway and they were Catalyst 2960s and Catalyst 3560s but I guess this discussion would help you in some way . Please do check the link for more information ( https://supportforums.cisco.com/message/3795974#3795974 )

Regards,
Anup

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