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colin
newbie
Topic Author
Posts: 29
Joined: Mon May 11, 2015 11:11 am

vrrp with mtu

Fri Dec 21, 2018 4:27 am

Does anyone know how to change mtu of vrrp interface?

The default value is 1500, and i change it to 1512 or 1480, but the actual mtu is still 1500

And it seems that it no effect to pppoe interface which created base on vrrp, for example:
eth1 mtu:1500
vrrp1 mtu:1460
pppoe1 mtu:1480
pppoe1 can connect successfully.
 
sathackr
just joined
Posts: 8
Joined: Thu Dec 25, 2014 5:13 am

Re: vrrp with mtu

Thu Jan 10, 2019 5:17 am

I'm seeing the same thing.

vrrp set on vlan interface.

physical inteface mtu is 10222
vlan interface mtu is 9170
vrrp interface mtu set to 9170 but actual mtu is 1500

this is on CCR-1072, RouterOS v6.42.11


config:
[admin@MikroTik1] > export compact
# jan/09/2019 19:30:00 by RouterOS 6.42.11
# software id = SYGW-LSV5
#
# model = CCR1072-1G-8S+
# serial number = XXXXXXXXXXXX
/interface ethernet
set [ find default-name=ether1 ] l2mtu=9116 mtu=9116
set [ find default-name=sfp-sfpplus1 ] l2mtu=10222 mtu=10222
set [ find default-name=sfp-sfpplus2 ] disabled=yes l2mtu=10222 mtu=10222
set [ find default-name=sfp-sfpplus3 ] disabled=yes l2mtu=10222 mtu=10222
set [ find default-name=sfp-sfpplus4 ] disabled=yes l2mtu=10222 mtu=10222
set [ find default-name=sfp-sfpplus5 ] disabled=yes l2mtu=10222 mtu=10222
set [ find default-name=sfp-sfpplus6 ] disabled=yes l2mtu=10222 mtu=10222
set [ find default-name=sfp-sfpplus7 ] disabled=yes l2mtu=10222 mtu=10222
set [ find default-name=sfp-sfpplus8 ] disabled=yes l2mtu=10222 mtu=10222
/interface vlan
add interface=sfp-sfpplus1 mtu=9170 name=vlan100-L3_MX960 vlan-id=100
/interface vrrp
add interface=vlan100-L3_MX960 interval=200ms mtu=9170 name=vrrp1 \
    priority=101 vrid=101
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/ip address
add address=10.10.7.5 interface=vrrp1 network=10.10.7.5
add address=10.10.7.2/29 interface=vlan100-L3_MX960 network=10.10.7.0
/ip route
add distance=1 gateway=10.10.7.1
/system clock
set time-zone-name=America/Chicago
/system identity
set name=MikroTik1
[admin@MikroTik1] >
 
sathackr
just joined
Posts: 8
Joined: Thu Dec 25, 2014 5:13 am

Re: vrrp with mtu

Thu Jan 10, 2019 5:20 am

Appears to be just cosmetic.

8000 byte ping packet works when sourced from vrrp IP address with do-not-fragment set.
[admin@MikroTik1] > ping 10.10.7.1 size=8000 do-not-fragment src-address=10.10.7.5
  SEQ HOST                                     SIZE TTL TIME  STATUS
    0 10.10.7.1                                8000  64 1ms
    1 10.10.7.1                                8000  64 1ms
    2 10.10.7.1                                8000  64 1ms
    3 10.10.7.1                                8000  64 1ms
    4 10.10.7.1                                8000  64 1ms
    5 10.10.7.1                                8000  64 1ms
    6 10.10.7.1                                8000  64 1ms
    7 10.10.7.1                                8000  64 1ms
    8 10.10.7.1                                8000  64 1ms
    sent=9 received=9 packet-loss=0% min-rtt=1ms avg-rtt=1ms max-rtt=1ms

[admin@MikroTik1] >
 
rendrag
just joined
Posts: 13
Joined: Tue May 20, 2014 12:31 am

Re: vrrp with mtu

Thu May 09, 2019 12:17 am

Appears to be just cosmetic.

8000 byte ping packet works when sourced from vrrp IP address with do-not-fragment set.
It's more than cosmetic. It appears like a bug. Try pinging TO the vrrp IP address, FROM the non-VRRP IP on the same router.. It enforces the 'cosmetic' MTU :(

i.e.

vlan39 - mtu 9100
vlan39_vrrp - mtu1500

Can ping vlan39 from vlan39_vrrp at 9100 no problem
Can ping vlan39_vrrp from vlan39 on another host at 9100 no problem.
Try to ping vlan39_vrrp from vlan39 at 9100 on same router? Frag needed

Hmmmmm :(

(RB1100AHx4 and RouterOS 6.44.3)
 
rendrag
just joined
Posts: 13
Joined: Tue May 20, 2014 12:31 am

Re: vrrp with mtu

Thu May 09, 2019 9:53 am

Whoa, and speaking of VRRP bugs, you can't have more than one IPv6 address on a VRRP interface, or they both stop communicating.. Same with having an IPv6 address on the VRRP interface, and on the parent interface. What the?!?

Actually, after some testing, when you set the V3 Protocol to IPv6, it then allows multiple IPv6 addresses *on* the VRRP interface. But if you also put a v6 IP on the parent interface (which is a standard config with VRRP yes??), then you lose v6 connectivity on that interface.. Hmmmm

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