topic Re: FTD 1010 with /31 Interface in Network Security

FTD 1010 with /31 Interface

Othacon — Tue, 19 Nov 2024 12:08:24 GMT

Hi all,

hope you can advise

I have my ISP giving me a /31 for my point to point link, but when inserting on the 1010 it gives me that I can't use a network as my IP address. I'm not using the FMC but the Firewall Device Manager since I only have a single firewall.

Is there any way maybe configuring a flex config object that would allow me to configure a /31 ip for my Wan interface?

Thank you

Re: FTD 1010 with /31 Interface

Flavio Miranda — Tue, 19 Nov 2024 12:38:54 GMT

@Othacon

Which version is this ?

Re: FTD 1010 with /31 Interface

Mark Elsen — Tue, 19 Nov 2024 12:40:27 GMT

- FYI : https://community.cisco.com/t5/network-security/firepower-ftd-2110-31-ip/m-p/3912288/highlight/true#M939371

Re: FTD 1010 with /31 Interface

MHM Cisco World — Tue, 19 Nov 2024 14:14:42 GMT

As I know this FTD limitations' you can not use prefix/31 in ftd because it have only one IP for host' you need to use /30

MHM

Re: FTD 1010 with /31 Interface

Othacon — Tue, 19 Nov 2024 19:44:52 GMT

@Flavio Mirandai've updated to the latest Version 7.6, but still it doesn't accept

Re: FTD 1010 with /31 Interface

Othacon — Tue, 19 Nov 2024 19:46:34 GMT

I did see this thread and saw below that there's a reply saying the latest versions do indeed accept but my 1010 simply won't accept it... if I put a /31 ip the FTD throws an error and doesn’t accept thread change.

Re: FTD 1010 with /31 Interface

Othacon — Tue, 19 Nov 2024 19:49:08 GMT

We really just need one ip per host, maybe this FTD doesn't really have the option?

Re: FTD 1010 with /31 Interface

MHM Cisco World — Tue, 19 Nov 2024 19:55:04 GMT

https://quickview.cloudapps.cisco.com/quickview/bug/CSCvg80765

Re: FTD 1010 with /31 Interface

Othacon — Tue, 19 Nov 2024 19:59:13 GMT

Thank you @MHM Cisco World , this is indeed weird, I get the "error message" that is in the bug description but my FTD has the version 7.6 and not the 6.x reported on the bug. Interesting

Re: FTD 1010 with /31 Interface

Flavio Miranda — Tue, 19 Nov 2024 20:21:05 GMT

@Othacon as per the documentation FTD still dont support /31 and FMC supports after 7.0

Re: FTD 1010 with /31 Interface

Othacon — Tue, 19 Nov 2024 20:23:20 GMT

Thank you @Flavio Miranda , since I don't have FMC, I won't be able to configured this.

Re: FTD 1010 with /31 Interface

OBXLife — Sat, 01 Feb 2025 12:39:01 GMT

There is ENH | Configure /31 on Firepower managed by FDM opened on this. Cisco not supporting a RFC on the Firepower that they co-wrote. RFC3021.