# Router advertisement with MTU 1280



## hrsahu (Sep 30, 2013)

Hi all,

I have a FreeBSd FreeBSD machine which acts a IPv6 router and it is able to send Route Advertisements to different hosts. I have included route advertisement details to the /etc/route.conf. But *I* want to know how to send a route advertisement with an MTU size of 1280. I add MTU details to the rc.conf file for a*n* interface.


```
ifconfig_re0_ipv6="inet6 2001:db8:ffff:2::201 prefixlen 64 mtu 1280"
```

And I also add the MTU value to /etc/rtadvd.conf:

```
re0:\
     :addr1="2001:db8:ffff:2::":prefixlen#64:mtu#1280:
```
but while checking with Wireshark, *I* can't see the route advertisement with MTU value. *C*ould you please tell me how to transmit a Route Advertisement with an MTU value of 1280?

Regards


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## bbzz (Sep 30, 2013)

Maybe because the MTU value is not carried in the packets. TCP MSS, on the other hand, is.


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## hrsahu (Oct 1, 2013)

Hi all,

Could you please tell me how TCP MSS will help to transmit IPv6 route advertisement with a option field of MTU size?

Regards


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## SirDice (Oct 1, 2013)

Have you tried setting it to auto in rtadvd.conf?


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