Description

This article describes the issue of a duplicate IP address being present on multiple SRX interfaces.

Symptoms

Duplicate IP address in the same network can be assigned to different SRX interfaces; however, the address is assigned to only one interface and in certain cases, a warning message is added to /var/log/messages .

Solution


The following tests were performed:

[edit]
SRX# set interfaces ge-1/0/0 unit 0 family inet address 3.3.3.3/24

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SRX# set interfaces ge-1/2/0 unit 0 family inet address 3.3.3.3/24

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SRX# show | compare
Feb 08 00:55:33
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+ interfaces {
    + ge-1/0/0 {
        + unit 0 {
            + family inet {
                + address 3.3.3.3/24;
            + }
        + }
    + }
+ ge-1/2/0 {
    + unit 0 {
        + family inet {
            + address 3.3.3.3/24;
        + }
    + }
+ }
+ }

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SRX#

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SRX# run show interfaces terse | match ge
Feb 08 00:56:12
ge-1/0/0 up down
ge-1/0/0.0 up down inet 3.3.3.3/24
ge-1/2/0 up down
ge-1/2/0.0 up down inet
ge-1/3/0 up down
From file /var/log/messages :
Feb 8 00:56:03 meenachil dcd[1593]: Warning: identical local address is found on default route instance, intf: ge-1/2/0.0, family t
ype: inet
Feb 8 00:56:03 meenachil dcd[1593]: DCD_PARSE_WARN_INCOMPATIBLE_CFG: [edit interfaces ge-1/2/0 unit 0 family inet address 3.3.3.3/2
4] : Incompatible configuration detected : identical local address is found on different interfaces
Feb 8 00:56:03 meenachil ffp[1604]: "dynamic-profiles": No change to profiles
Feb 8 00:56:04 meenachil dcd[1536]: Warning: identical local address is found on default route instance, intf: ge-1/2/0.0, family t
ype: inet


SRX# run show interfaces terse | match ge
Feb 08 01:01:07
ge-1/0/0 up down
ge-1/0/0.0 up down inet 10.192.128.1/26
ge-1/2/0 up down
ge-1/2/0.0 up down inet 10.192.128.2/26
ge-1/3/0 up down

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SRX#
From /var/log/messages files:
Feb 8 01:00:58 meenachil dcd[1677]: Warning: identical subnet address 10.192.128.2/26 is found on default route instance, intf: ge-
1/2/0.0, family type: inet
Feb 8 01:00:58 meenachil dcd[1677]: DCD_PARSE_WARN_INCOMPATIBLE_CFG: [edit interfaces ge-1/2/0 unit 0 family inet address 10.192.12
8.2/26] : Incompatible configuration detected : identical subnet 10.192.128.2/26 is found on ge-1/0/0
Feb 8 01:00:58 meenachil ffp[1688]: "dynamic-profiles": No change to profiles
Feb 8 01:00:59 meenachil dcd[1536]: Warning: identical subnet address 10.192.128.2/26 is found on default route instance, intf: ge-
1/2/0.0, family type: inet
However, when different IFLs under the same IFD are configured with addresses in the same subnet, the configuration is applied and no messages are generated in the /var/log/messages file:
SRX# set interfaces ge-1/0/0 vlan-tagging

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SRX# set interfaces ge-1/0/0 unit 0 vlan-id 1

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SRX# set interfaces ge-1/0/0 unit 0 family inet address 10.10.10.1/24

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SRX# set interfaces ge-1/0/0 unit 1 vlan-id 2

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SRX# set interfaces ge-1/0/0 unit 1 family inet address 10.10.10.2/24

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SRX# show | diff
Feb 08 01:05:54
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+ interfaces {
    + ge-1/0/0 {
        + vlan-tagging;
        + unit 0 {
            + vlan-id 1;
            + family inet {
                + address 10.10.10.1/24;
            + }
        + }
+ unit 1 {
    + vlan-id 2;
    + family inet {
        + address 10.10.10.2/24;
    + }
+ }
+ }
+ }

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SRX#

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SRX# commit
Feb 08 01:06:07
commit complete

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SRX# run show interfaces terse | match ge
Feb 08 01:06:15
ge-1/0/0 up down
ge-1/0/0.0 up down inet 10.10.10.1/24
ge-1/0/0.1 up down inet 10.10.10.2/24
ge-1/0/0.32767 up down
ge-1/2/0 up down
ge-1/3/0 up down

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SRX#

But when the same address is added to different IFLs under the same IFD, the commit fails:
SRX# set interfaces ge-1/0/0 vlan-tagging

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SRX# set interfaces ge-1/0/0 unit 0 vlan-id 1

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SRX# set interfaces ge-1/0/0 unit 0 family inet address 10.10.10.1/24

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SRX# set interfaces ge-1/0/0 unit 1 vlan-id 2

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SRX# set interfaces ge-1/0/0 unit 1 family inet address 10.10.10.1/24

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SRX# show | diff
Feb 08 01:07:48
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+ interfaces {
    + ge-1/0/0 {
        + vlan-tagging;
        + unit 0 {
            + vlan-id 1;
            + family inet {
                + address 10.10.10.1/24;
            + }
        + }
+ unit 1 {
    + vlan-id 2;
    + family inet {
        + address 10.10.10.1/24;
    + }
+ }
+ }
+ }

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SRX#

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SRX# commit
Feb 08 01:08:25
[edit interfaces ge-1/0/0 unit 1 family inet]
'address 10.10.10.1/24'
Cannot have the same local address on different units of an interface
error: configuration check-out failed

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SRX#