I have a routerboard with two ports bridged together. Under the bridge I add a vlan. Running OSPF on the router. If I reboot the router I start getting this error:
Discarding database description packet: too large MTU mine=1458 received=1500
If I check the MTU of the vlan it is set to 1500.
As soon as I disable the vlan and re-enable it the problem goes away. It doesn't seem to reappear unless I reboot.
Hardware CCR-1009-8G-1S running 6.30.1
Re: VLAN MTU issue
Hello
I have a similar problem (6.47.1, "cAP ac" with IP 100.64.5.197 and NAT):
"/interface vlan set 0 mtu=1542 " seems to fix the problem, but it looks strange.
I have a similar problem (6.47.1, "cAP ac" with IP 100.64.5.197 and NAT):
Code: Select all
11:08:48.574235 IP x.x.x.6.https > 100.64.5.197.34552: Flags [.], seq 1:1461, ack 518, win 30016, length 1460
11:08:48.574836 IP 100.64.5.197 > x.x.x.6: ICMP 100.64.5.197 unreachable - need to frag (mtu 1458), length 556
Code: Select all
/interface vlan
add interface=ether1 name=ether1.608 vlan-id=608
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/interface vlan pr
Flags: X - disabled, R - running
# NAME MTU ARP VLAN-ID INTERFACE
0 R ether1.608 1500 enabled 608 ether1"/interface vlan set 0 mtu=1542 " seems to fix the problem, but it looks strange.
Last edited by asy on Mon Jul 27, 2020 6:15 pm, edited 2 times in total.
Re: VLAN MTU issue
"/interface vlan set 0 mtu=1542 " seems to fix the problem
But it can probably cause traffic problems from the router itself.
Last edited by asy on Wed Jul 29, 2020 9:00 am, edited 1 time in total.
Re: VLAN MTU issue
"/interface vlan set 0 mtu=1542 " seems to fix the problem, but it looks strange.
Even more interesting. The router had in the initial configuration
Code: Select all
> interface br pr
Flags: X - disabled, R - running
0 R ;;; defconf
name="bridge" mtu=auto actual-mtu=1458 l2mtu=1594 ...and internal and used ether1.001 included to it:
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/interface bridge port
add bridge=bridge comment=defconf interface=ether2
add bridge=bridge comment=defconf interface=wlan1
add bridge=bridge comment=defconf interface=wlan2
add bridge=bridge interface=ether1.001
"interface br set 0 mtu=1500" solve the problem also (without increasing MTU on an external ether1. 608).
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