Supervlan and needless DHCP Requests

[Victor_Vit]

Hello.

If I use separate vlans on Extreme X450-24 ver. 15.3.5.2 with bootprelay, DHCP works fine for my client-device. At first there are DhcpDiscover,DhcpOffer,DhcpRequest and DhcpAck and than there are one DhcpRequest + one DhcpAck during right time-period. All right.

But if I begin to use supervlan, the situation is changed. My device sends one DhcpRequest but receives 2 replays.

Scheme:
client-device <-> switch <-> extreme witch supervlan and bootprelay <-> DHCP server

When I have mirrored traffic between switch and extreme I have seen so situation (by tcpdump):
17:20:51.442246 IP client_ip.68 > dhcp_server_ip.67: BOOTP/DHCP, Request from e8:94:f6:53:cf:45, length 548
17:20:51.442803 IP dhcp_server_ip.67 > client_ip.68: BOOTP/DHCP, Reply, length 300
17:20:51.443525 IP dhcp_server_ip.67 > client_ip.68: BOOTP/DHCP, Reply, length 300

When I have mirrored traffic between extreme and DHCP server I have seen other situation (by tcpdump):
16:08:21.422645 IP client_ip.bootpc > dhcp_server_ip.bootps: BOOTP/DHCP, Request from e8:94:f6:53:cf:45, length 548
16:08:21.423216 IP dhcp_server_ip.bootps > client_ip.bootpc: BOOTP/DHCP, Reply, length 300
16:08:21.423477 IP client_ip.bootpc > dhcp_server_ip.bootps: BOOTP/DHCP, Request from e8:94:f6:53:cf:45, length 548
16:08:21.424140 IP dhcp_server_ip.bootps > client_ip.bootpc: BOOTP/DHCP, Reply, length 300

So, after extreme we have duplicate of DhcpRequest packet.
I think extreme makes it. Why does it make this?

I have used also dhcpdump on DHCP server, but both Requests are identical

How can I fix this situation?

Thank you.

[Alexandr_P]

Also:
dhcp relay work at L3,
at L2 work dhcp snooping.
If your subvlans have no IP-addresses - it's can be as a part of issue. (just in theory)

Thank you!

[Alexandr_P]

Subvlan IP addresses from Supervlan addresses range.
You take it from main supervlan IP range, or from secondary IP range?
(because there is restriction)

Thank you!

[Victor_Vit]

I'm sorry, but I didn't understand your question. What do you mean by “address range in subvlan”? Please, explain it.
We have such ranges in supervlan:
configure vlan SU ipaddress *.*.*.1 255.255.255.128
configure vlan SU add secondary-ipaddress *.*.*.129 255.255.255.128
I'm sorry, but we don't want to show our real ip for all.

Thank you!

[Alexandr_P]

What address range is using in subvlan?

Thank you!

[Victor_Vit]

Hello, Alexandr.

Client 's device (TP-link wr740n or Windows 7) is connected to management switch. Client's vlan (one of subvlans on 450) is untagged on client's port and on port that this switch is connected to extreme 450. On extreme 450 there are 2 subvlans in 1 supervlan.
Bootprelay is on in all vlans. (when I off bootprelay — It didn't make any effect ).
This 450 is connected by ospf with extreme 650.
On 650 bootprelay is also on in vlan with it 450 and 650 are connected, and 650 has direct interface(separate vlan with bootprelay) to DHCP server.

Supervlan on 450
create vlan "SU"
configure vlan SU ipaddress *.*.*.1 255.255.255.128
enable ipforwarding vlan SU
configure vlan SU add secondary-ipaddress *.*.*.129 255.255.255.128
configure vlan "SU" add subvlan "test-su-2"
configure vlan "SU" add subvlan "test-su-1"
enable bootprelay vlan SU
configure ospf add vlan SU area 0.1.1.1 passive

Bootprelay:
configure bootprelay add *.*.*.* vr VR-Default
enable bootprelay vlan SU
enable bootprelay vlan km (vlan to 650)
enable bootprelay vlan test-su-1
enable bootprelay vlan test-su-2