Two IPs with different netmask on the same vlan


Can i add two ip in the same vlan?

My Black Diamond (BD8810) have his management interface on my vlan50 with netmask 255.255.0.0 (/16) and i have one Cisco that have the same vlan50 with netmask 255.0.0.0 (/8) but for other network.

I want to move the uplink of this other network to my BD. But the users of the other network need to check my "switch" SNMP via vlan50/8.

So, if i can use two VLAN50 ip address, one with /16 and other with /8 mask i can start to remove the cisco switch.

I know that i will have another problem in the future. That is to block all my traffic from VLAN50/16 to go to VLAN50/8 port. We already do this with the cisco switch, by blocking mac addresses.

11 replies

Userlevel 6
Hi Gerson, please see the article below:

https://gtacknowledge.extremenetworks.com/articles/Q_A/Is-it-possible-to-configure-secondary-IP-addr...

An option would be using another Virtual-router (VR)

https://gtacknowledge.extremenetworks.com/articles/Q_A/What-is-a-Virtual-Router
Userlevel 4
What i feel this feature is not supported on EXOS. Well as stated by Henrique you can avail the facility of using the VR concept. This may help you in achieving the same.
Ok. I'm going to study this feature and try.

Thanks.
I am assuming vlan50 on the BD and Cisco switch are different and you don't want the users talking? If that isn't the case, proxy arp might take care of some of this.
@Henrique,
create vlan TEST-VL50 vr "VR-TEST" tag 50

Error: 802.1Q Tag 50 is assigned to VLAN vlan50.

I can't create another vlan using the same vlanID 😕

And i need it to be the same ID "50" because my switch is part of one ring using this tagged vlan.
The VID is the vlan, so if you already created it, why would you need to make it again?
Cos, i want to add two ip in the same vlan. And@Henrique told me to create another virtual route.
Userlevel 6
gbs wrote:

Cos, i want to add two ip in the same vlan. And@Henrique told me to create another virtual route.

Hi Gerson, you can use the same ipaddress/subnet in different VRs. However, you cannot use the same VRID since the vlan table is shared between VRs.
Userlevel 7
Hi Gerson,

are the two "VLAN 50" networks overlapping? For example, 10.0.0.0/8 and 10.55.0.0/16 are overlapping networks. You cannot use a secondary IP address in this case. In fact, for overlapping IP networks you need different virtual routers (VRs), not just different VLANs.

If the networks are not overlapping, e.g. 10.0.0.0/8 and 172.20.0.0/16, then you can use a secondary IP address on VLAN 50. Please see the GTAC Knowledge article How to add secondary IP address on a VLAN.

To get around the problem of having the same VLAN ID for two networks with overlapping IP address ranges, you could add another switch in front of the BD to translate the VLAN tag, using e.g. port specific VLAN tags. Please see Does EXOS support Port-Specific VLAN Tag? and How to configure port specific tags.

Erik
Erik Auerswald wrote:

Hi Gerson,

are the two "VLAN 50" networks overlapping? For example, 10.0.0.0/8 and 10.55.0.0/16 are overlapping networks. You cannot use a secondary IP address in this case. In fact, for overlapping IP networks you need different virtual routers (VRs), not just different VLANs.

If the networks are not overlapping, e.g. 10.0.0.0/8 and 172.20.0.0/16, then you can use a secondary IP address on VLAN 50. Please see the GTAC Knowledge article How to add secondary IP address on a VLAN.

To get around the problem of having the same VLAN ID for two networks with overlapping IP address ranges, you could add another switch in front of the BD to translate the VLAN tag, using e.g. port specific VLAN tags. Please see Does EXOS support Port-Specific VLAN Tag? and How to configure port specific tags.

Erik

It worked! Thanks 😃
Yes, they are overlapping. I want to use my 10G module of BD8810 for that. I will check that port specific vlan tag thing. Thanks.

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