Two VLANs with different MTUs?

McMurphy

LAN Interface (lan, xn1)
Status
up 
MAC Address
06:94:68:23:79:2e
IPv4 Address
10.40.1.254
Subnet mask IPv4
255.255.255.0
IPv6 Link Local
fe80::494:68ff:fe23:792e%xn1
MTU
1504
Media
manual
In/out packets
3509789179/3789620003 (4.56 TiB/4.54 TiB)
In/out packets (pass)
3509789179/3789620003 (4.56 TiB/4.54 TiB)
In/out packets (block)
54/0 (41 KiB/0 B)
In/out errors
0/0
Collisions
0

VL1000 Interface (opt1, xn1.1000)
Status
up 
MAC Address
06:94:68:23:79:2e
IPv4 Address
10.54.0.14
Subnet mask IPv4
255.255.255.240
IPv6 Link Local
fe80::494:68ff:fe23:792e%xn1.1000
MTU
1496
Media
manual
In/out packets
1931870/2499576 (538.41 MiB/1.54 GiB)
In/out packets (pass)
1931870/2499576 (538.41 MiB/1.54 GiB)
In/out packets (block)
285/0 (59 KiB/0 B)
In/out errors
0/2629
Collisions
0

VL1007 Interface (opt17, xn1.1007)
Status
up 
MAC Address
06:94:68:23:79:2e
IPv4 Address
10.54.0.126
Subnet mask IPv4
255.255.255.240
IPv6 Link Local
fe80::494:68ff:fe23:792e%xn1.1007
MTU
1500
Media
manual
In/out packets
49296319/41174216 (27.35 GiB/8.17 GiB)
In/out packets (pass)
49296319/41174216 (27.35 GiB/8.17 GiB)
In/out packets (block)
9168/0 (815 KiB/0 B)
In/out errors
0/1238
Collisions
0

Neither VLAN has an MTU specified in the interface.

netblues

@McMurphy On what hardware are you on? Anything virtualized?

McMurphy

@netblues

pfSense is virtualised on Xen Server

netblues

@McMurphy Then most probably it inherits the mtu from the xen bridges, which is expected.

McMurphy

@netblues

Even if both VLANs are on the same interface?

netblues

@McMurphy Well, its common to configure the native lan with eg jumbo frames ~9000 and then specify smaller mtu for vlans.
1504 is common to support native 1500 mtu on pppoe.

I suppose the interface is not in passthrough to pf, just bridges.

I can't say how xen exaclty handles this, but in kvm is as above.