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The interface the ProxySG uses for default route and how to change it

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Article ID: 173272

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Updated On:

Products

Advanced Secure Gateway Software - ASG ProxySG Software - SGOS

Issue/Introduction

If multiple interfaces have ip addresses from the same subnet and the default GW is also on the same subnet range, which interface will be used.
The ProxySG always picks the lowest interface ID for default route.

Environment

Example:

interface 0:0: 172.168.10.5/24
interface 1:0: 192.168.10.100/24
interface 2:0: 192.168.10.20/24
ip-default-gateway: 192.168.10.1
ProxySG automatically selects interface 1:0 for traffic going to default gateway.

Routing Table can be obtained from sysinfo:TCP/IP Routing Table, or CLI "show ip-route". The following Routing Table shows Netif 1:0 is used for default route.

; TCP/IP Routing Table
Routing tables

Routing domain default
Internet:
Destination       Gateway            Flags    Refs      Use        Netif   Expire
default           192.168.10.1       UGS      3570 100033341         1:0
127.0.0.1         127.0.0.1          UH          2    41999     loopback
172.168.10.0/24   link#3             UC          0        0          0:0 =>
172.168.10.0/24   172.168.10.1       UGS         1        0          0:0
172.168.10.1      00:08:e3:ff:fc:28  UHLW        2        0          0:0      105
172.126.24.0/24   172.168.10.1       UGS         1        0          0:0
192.168.10.0/24   link#4             UC          0        0          1:0 =>
192.168.10.0/24   link#5             UC          0        0          2:0
192.168.10.1      6c:b2:a1:ab:c1:0d  UHLW       10  3482374          1:0       50
192.168.10.2      70:0f:5a:f8:70:ad  UHLW        0  3482115          1:0      433

Resolution

The only way to force the ProxySG to use a different interface than the current interface for default route is to disable the current interface.
ProxySG will select the next lowest ID interface for default route.

In our example, after interface 1:0 is disabled, routing table will be updated and changed to Netif=2:0 for default route.
Once the routing table is changed, enabling interface 1:0 does not make routing table revert back.
However, whenever the ProxySG reboots, interface 1:0 will be selected for default again.