FTD 1010 with /31 Interface

[Othacon]

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

[Flavio Miranda]

@Othacon 

Which version is this ?

[Othacon]

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

[Flavio Miranda · Accepted solution]

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

[Othacon]

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

[marce1000]

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

  M.

[Othacon]

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.

[MHM Cisco World]

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

[Othacon]

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

[MHM Cisco World]

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

[Othacon]

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

[OBXLife]

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.