SRX

Hello

I was on an working SRX 1500 chassis cluster and could see the em1.32768 interface with IP 192.168.1.2/24.

The SRX 1500 has a dedicated HA control port which is em0.

On the bigger chassis, like the 3400, I see a couple of ports on the far right of the switch fabric board (SFB) called 'Chassis cluster control' 0 and 1.

But the cabling article here shows you only use port 0 on the 3400 - https://www.juniper.net/documentation/en_US/junos/topics/task/operational/chassis-cluster-srx-series-hardware-connecting.html

This article - https://kb.juniper.net/InfoCenter/index?page=content&id=KB15356 - says to use:

Chassis Cluster Control
Port 0 (copper or fiber) on SFB    => em0
Port 1 (copper or fiber) on SFB    => em1 

(Which appears to contradict  https://www.juniper.net/documentation/en_US/junos/topics/task/operational/chassis-cluster-srx-series-hardware-connecting.html ?)

And this article - https://kb.juniper.net/InfoCenter/index?page=content&id=KB21706&cat=SRX_5600_1&actp=LIST - says there is no correlation between em0 and em1 and physical ports.

I'm confused...

Any further explanation would be great, and also if someone can tell me specifically what em1.32768 is on the SRX1500 chassis cluster I'd appreciate it.

Thanks!

Hi!

Below is how you need to cable it up for a SRX1500.

KR

Adam

Hi,

Thanks for taking the time to reply but this isn't the answer to the question 🙂

Just to clarify, the SRX pair I was working on are in production, cabled up correctly and operating normally with the expected interfaces present in the output... I just was intruiged by the purpose of/reason for the em1.32768 interface and looking for more information on it

Hi username,

In branch SRX devices the:

     fxp0 is the management interface
     fxp1 is the control-link connection between the devices

In High End SRX platforms the:

     fxp0 is the management interface
    em0 and em1 are the control-link connections between the devices. Note some of these platforms support dual-control link and this is why you see em0 and em1, each one representing one of the two control-links that could exist.

Note the document you provided for SRX3K is not considering a ascenario with dual control-link hence only one of the HA ports on the SFB is used in figure 14:

https://www.juniper.net/documentation/en_US/junos/topics/task/operational/chassis-cluster-srx-series-hardware-connecting.html

I am confirming the validity of KB21706 because em0 and em1 represent the control-link in HE SRXs. See the output of "show chassis cluster interfaces" for a SRX5800 and a SRX1500 cluster in the following link:

https://www.juniper.net/documentation/en_US/junos/topics/topic-map/security-chassis-cluster-active-passive-deployments.html#id-example-configuring-an-activepassive-chassis-cluster-pair-cli

Great explanation!. 

Kudos

username,

Final answer is:

“em0 and em1 are internal communications to the RE as stated in KB21706.

Because the control-link ports are used for communication between the REs in a cluster, in SRX1500 and SRX4K they are linked to em0 which is the internal link used for communication of REs for cluster purposes. However the physical status of the control-link ports don’t necessarily relate to the status of em0 link and vice versa.

Interface em1.32768 is a subunit of em1 that is used for internal communications between the RE and other components, for instance for communications with the linux host OS on which the Junos runs as a vm.”

I hope the above information answer your question.

Hi username

I was wondering if my last comment answered your question in which case the post could be marked as Resolved.

Thank you!