Summary: 2 interfaces, one shared subnet

From: Earl R Cooke (
Date: Tue Dec 14 1999 - 17:36:01 CST

Thanks for all the fast responses.
Using Sun's virtual Interface is the best solution.
I configured it, and for some unknown reason, neither interface got initialized
during the first reboot. I logged in at the console, looked around, but
couldn't find anything misconfigured, rebooted again, and everything works.
Works on subsequent reboots as well. Routing tables show two entries for the
local net, but it doesn't seem to cause a problem as it did before.

Apparently Solaris automatically provides load balancing between the two

Helpful responses received from:

Al Quinlan
Mike Allmen
Buddy Lumpkin
deepak Sinha
Roger Fujii
Craig Russell
Ian Evans

Sample response from Buddy:

You need a virtual Interface. If your primary interface is /etc/hostname.hme0
then create a /etc/hostname.hme0:1
edit this file and add a hostname, usually a good choice for a hostname is the
hostname with like a -1 at the end so if your machine is called kenny edit
/etc/hostname.hme0:1 and on the first line put kenny-1. Then make a
entry in /etc/hosts like this:
#lets say this is the ip of the first interface: kenny kenny-1

on reboot, kenny-1 would be added on the same subnet and not extra physical
interface is needed. You can also bring this interface up using ifconfig hme0:1
plumb and all other associated ifconfig commands.

On another note, there is a patch for Solaris 2.6 that fixes some minor issues
have to do with multiple interfaces, its 105786-08.

Also, if you are dealing with a firewall and web servers, you may find yourself
setting this in /etc/system:

* Added by Buddy Lumpkin to fix strange behavior of Solaris 2.6 virtual ip's
set ip:ip_enable_group_ifs = 0

This stops the Round-Robin effect that Solaris 2.6 uses by default for load
balancing, etc..


Earl R Cooke wrote:

> Same message, with subject! sorryaboutthat.
> Admins,
> I have a Sun 3500 running Solaris 2.6. I need to enable a second hme
> interface on this node,
> problem is both are on the same shared subnet..
> When I edit the /etc/hostname.hmeX, and /etc/hosts files and reboot,
> the second interface comes on-line, but the routing tables get two entries for
> the local network,
> one showing each interface as the gateway. This causes the system to behave
> strangely,
> network connections work slowly, or not at all.
> Once I manually delete the second entry with the route command, the system
> fine.
> Is it NOT recommended to have two interfaces on the same shared subnet, or did
> leave a step off,
> or should I expect to have to manually remove this second route after each
> reboot?
> Also is there an easy way to get the first interface to respond to both IP's,
> this would solve my problem,
> as this is not a bandwidth issue?.
> Thanks in advance.
> Earl Cooke

This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:13:35 CDT