unable to set dhcp relay address on interface of an SG350XG-48T

[ddiguru]

I'm not able to set specific DHCP relay addresses on interfaces. I can only set them globally from the CLI. When i add them to an interface, they default to global even though i'm on a specific interface. Is this a bug or am i doing something wrong? 

Active-image: flash://system/images/image_tesla_hybrid_2.4.5.71_release_cisco_signed.bin
Version: 2.4.5.71
MD5 Digest: 2dff89efdb2a0ec2f9a2c414ff7d401c
Date: 04-Nov-2018
Time: 19:46:16

I've tried clearing out all globals and starting from scratch, but to no avail. 

DHCP relay is Disabled
Option 82 is Disabled
Maximum number of supported VLANs without IP Address is 256
Number of DHCP Relays enabled on VLANs without IP Address is 0
DHCP relay is not configured on any port.
DHCP relay is enabled on Vlans: 1,20,50,60,70
Active:
Inactive: 1,20,50,60,70
Servers: 192.168.3.27 , 192.168.3.28

I tried to add 192.168.4.40 as a DHCP relay to interface VLAN 10:

cisco01(config)#interface vlan 10
cisco01(config-if)#ip dhcp relay address 192.168.4.40
cisco01(config-if)#ip dhcp relay enable
cisco01(config-if)#exit
cisco01(config)#exit

show run | inc dhcp shows the server got added to the global list instead of to the interface

Please advise... Thanks!

[Jaderson Pessoa]

Hello,

I have dhcp relay enable without problem, may it is a bug os your system. You can apply it on physical interface and/or vlan interface.

DHCP relay is Enabled
Option 82 is Disabled
Maximum number of supported VLANs without IP Address is 256
Number of DHCP Relays enabled on VLANs without IP Address is 0
DHCP relay is not configured on any port.
DHCP relay is enabled on Vlans: 15-16,18,20-29
Active: 15-16,18,20-29
Inactive:
Servers: 172.20.14.196 , 172.20.14.198 , 172.20.14.211

Active-image: flash://system/images/image_tesla_hybrid_2.4.0.94.bin
Version: 2.4.0.94
MD5 Digest: 6f5be217100f34929986f2e93dd2d5e9
Date: 31-May-2018
Time: 02:39:58

Regards.

[Jaderson Pessoa]

DHCP relay is Disabled    << your dhcp relay is disabled.
Option 82 is Disabled
Maximum number of supported VLANs without IP Address is 256
Number of DHCP Relays enabled on VLANs without IP Address is 0
DHCP relay is not configured on any port.
DHCP relay is enabled on Vlans: 1,20,50,60,70
Active:
Inactive: 1,20,50,60,70
Servers: 192.168.3.27 , 192.168.3.28

 try it:

SWC(config)#ip dhcp relay enable

SWC(config)#ip dhcp relay address x.x.x.x

interface vlan 20

ip dhcp relay enable

interface vlan 50

ip dhcp relay enable

interface vlan 60

ip dhcp relay enable

interface vlan 70

ip dhcp relay enable

[ddiguru]

Jaderson, 

Yes, I had that enabled before... sorry. 

DHCP relay is Enabled
Option 82 is Disabled
Maximum number of supported VLANs without IP Address is 256
Number of DHCP Relays enabled on VLANs without IP Address is 0
DHCP relay is not configured on any port.
DHCP relay is enabled on Vlans: 1,20,50,60,70
Active: 1,20,50,60,70
Inactive:
Servers: 192.168.3.27 , 192.168.3.28

With .27 and .28 as global ip DHCP relay addresses, i'm not able to edit interface vlan 10 with a different specific DHCP relay address of 192.168.4.40. Any time I attempt to do so, it's simply added to the list of global DHCP relay servers. 

The only thing different is you're running older code than I am. I'm wondering if I can back down to that release and IF that fixes the issue?

[Jaderson Pessoa]

With .27 and .28 as global ip DHCP relay addresses, i'm not able to edit interface vlan 10 with a different specific DHCP relay address of 192.168.4.40. Any time I attempt to do so, it's simply added to the list of global DHCP relay servers.  << you cant apply diffrent dhcp server per interface, you can configure dhcp scope for vlan 10 and set it as globally too. Its wil work normally. 

If you need that is restrited you can create a acl to filter the traffic.

The only thing different is you're running older code than I am. I'm wondering if I can back down to that release and IF that fixes the issue?   << its not necessary run downgrade.

[ddiguru]

So, based upon what you're telling me - this is a limitation of the SG350/SG550 platform vs Cisco IOS

I know this is possible on Cisco IOS. According to the CLI docs for SG250XG this SHOULD be possible. The docs read that you can set interface specific ip dhcp server address <x.x.x.x> on a physical, vlan or Port-Channel. 

[ddiguru]

This is what i would like to do:
1) remove global dhcp relay addresses

no ip dhcp relay address 192.168.3.27
no ip dhcp relay address 192.168.3.28
no ip dhcp relay address 192.168.4.40

2) add specific dhcp relay addresses to VLAN interfaces directly

interface vlan 1
ip dhcp relay address 192.168.3.27
ip dhcp relay address 192.168.3.28
ip dhcp relay enable
exit

interface vlan 20
ip dhcp relay address 192.168.3.27
ip dhcp relay address 192.168.3.28
ip dhcp relay enable
exit

interface vlan 50
ip dhcp relay address 192.168.3.27
ip dhcp relay address 192.168.3.28
ip dhcp relay enable
exit

interface vlan 60
ip dhcp relay address 192.168.3.27
ip dhcp relay address 192.168.3.28
ip dhcp relay enable
exit

interface vlan 70
ip dhcp relay address 192.168.3.27
ip dhcp relay address 192.168.3.28
ip dhcp relay enable
exit

interface vlan 10
ip dhcp relay address 192.168.4.40
ip dhcp relay enable
exit

[Jaderson Pessoa]

Thats ok.

Just remove the servers from globally configuration, but leave it active status and add each server per interface or vlan.

check it: i hope that it can help you.

https://www.cisco.com/c/en/us/support/docs/smb/switches/cisco-small-business-300-series-managed-switches/smb5567-configure-dynamic-host-configuration-protocol-dhcp-relay-set.html

Dont forget to mark as solved and helpful all post that were help you.

[ddiguru]

Yes, i saw that URL and tried following that. Just doesn't seem to work.

[Jaderson Pessoa]

Please, dont forget, when you apply it on interface. it is added automatically on global address. Doesn't matter if you remove it before, when you apply it on interface, it will be added at globally server as well. But it will be disponible just for that vlan.

Like it: interface vlan 26
name GUEST
ip address 172.20.23.1 255.255.255.0

ip dhcp relay address 172.20.14.196
ip dhcp relay enable

DHCP relay is Enabled
DHCP relay is enabled on Vlans: 15-16,18,20-29
Active: 15-16,18,20-29
Inactive:
Servers: 172.20.14.196 , 172.20.14.198 , 172.20.14.211

[ddiguru]

That makes no sense to me at all. I would expect:

global ip dhcp relay address <x.x.x.x> to apply to:

• The entire switch if you globally enable ip dhcp relay 
• specific interfaces with ip dhcp relay enable

I would expect the ability to set interface-specific ip dhcp relay address <x.x.x.x> on specific VLAN, interface or port-channel and for that value(s) to override global settings. I would also expect that interface-specific dhcp relay addresses would NOT be added to the global list. 

I expect that I should be able to add specific DHCP relay addresses that are specific to say VLAN 10, using a different value than what is stated globally. 

I think this is a software bug.

[Jaderson Pessoa]

Maybe, for my version it is working normally, At the same way there are any report bugs on your version, but you can try downgrade it to test.

[ddiguru]

Given what you wrote, what does your configuration look like if you do:

show run int vlan 26

and do you see 172.20.14.196 show up in the global list of servers OR does is it indented underneath interface VLAN 26?

[Jaderson Pessoa]

show run int vlan 26

interface vlan 26
name GUEST
ip address 172.20.23.1 255.255.255.0
ip dhcp relay enable
service-acl input REDEGUEST

if i remove it from global configuration and add dhcp address under interface.  Its add automatically to global configuration:

SWC#show ip dhcp relay
DHCP relay is Enabled
Option 82 is Disabled
Maximum number of supported VLANs without IP Address is 256
Number of DHCP Relays enabled on VLANs without IP Address is 0
DHCP relay is not configured on any port.
DHCP relay is enabled on Vlans: 15-16,18,20-29
Active: 15-16,18,20-29
Inactive:
Servers: 172.20.14.196 , 172.20.14.198 , 172.20.14.211

SWC(config)#no ip dhcp relay add 172.20.14.196

DHCP relay is Enabled
Option 82 is Disabled
Maximum number of supported VLANs without IP Address is 256
Number of DHCP Relays enabled on VLANs without IP Address is 0
DHCP relay is not configured on any port.
DHCP relay is enabled on Vlans: 15-16,18,20-29
Active: 15-16,18,20-29
Inactive:
Servers: 172.20.14.198 , 172.20.14.211

SWC(config)#int vlan 26
SWC(config-if)#ip dhcp relay address 172.20.14.196

DHCP relay is Enabled
Option 82 is Disabled
Maximum number of supported VLANs without IP Address is 256
Number of DHCP Relays enabled on VLANs without IP Address is 0
DHCP relay is not configured on any port.
DHCP relay is enabled on Vlans: 15-16,18,20-29
Active: 15-16,18,20-29
Inactive:
Servers: 172.20.14.196 , 172.20.14.198 , 172.20.14.211

Please, dont forget of mark as solved and helpful all post the were help you.

thanks in advance.

[ddiguru]

I'm sorry i didn't make myself clear. Instead of showing output from show ip dhcp relay can you provide the output from:

show run int vlan 26

I'm curious if it's listed under the interface or global list in the config. 

I know that they will all appear in the list of servers from the show ip dhcp relay, but i'm interested in knowing if you can put a custom server under an interface.