Help with MTU increase failure

m3atwad

New Member
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Hello,
I'm trying to increase my MTU to 9000 for my gigabit ethernet port. I can increase to 4000, but after that I get the following errors for all my ports.
Code:
SIOCSIFMTU: Operation not permitted
I've searched through the driver source and can't find the limitation in the driver. I'm using a Xilinx SoC running embedded linux so I'm wondering if this is limited somewhere in the kernel. Does anyone have any recommended paths to go down in order to trouble shoot this?

As a side note it looks like all my links would support an MTU of 9000 after running this command showing the max MTU sizes for eth1-eth4
Code:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 promiscuity 0 minmtu 0 maxmtu 0 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:0a:35:00:1e:53 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 1500 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
3: eth1: <BROADCAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:0a:35:00:01:22 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 64 maxmtu 9000 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
4: eth2: <BROADCAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:0a:35:00:1e:53 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 64 maxmtu 9000 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
5: eth3: <BROADCAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:0a:35:00:01:24 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 64 maxmtu 9000 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
6: eth4: <BROADCAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:0a:35:00:01:25 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 64 maxmtu 9000 addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
7: [email protected]: <NOARP> mtu 1480 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/sit 0.0.0.0 brd 0.0.0.0 promiscuity 0 minmtu 1280 maxmtu 65555
    sit ip6ip remote any local any ttl 64 nopmtudisc addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
Any help is greatly appreciated!
 


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