06-01-2019 10:45 AM
Hi, the FTD software (22.214.171.124) on ASA 5506-X does not seem to support point-to-point (/31) ipv4 subnets. When trying to set my static /31 public ip on the outside interface in FDM the error message "You cannot assign a broadcast address as the IP address of an interface" is raised. A fix would be most appriciated !
06-01-2019 01:33 PM
This message is clearly says you can not assign ""You cannot assign a broadcast address as the IP address of an interface"
can you please show us more information, what is the exactly IP address you trying to Assign ?
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06-02-2019 03:18 AM
Hi, any attempt to assign an ip address with netmask 255.255.255.254 to an interface in FDM will either raise the error message above or "You cannot assign a network address "x.x.x.x/255.255.255.254" as the IP address of an interface" based on whether you are using the first or last address in the point-to-point subnet.
/31 subnets is not a problem on a IOS router or ASA:
ip address x.x.x.81 255.255.255.254
06-02-2019 04:31 AM
I just tried that on my FPR 2110 and it does work. What's the extact IPv4 address you are entering?
06-02-2019 09:18 AM
I'm using a new ASA5506-X reimaged with FTD and FDM local management (no FMC avail). The smallest subnet possible on the interfaces is /30. If the problem is FDM, could the interface ip be configured from CLI Expert mode ?
06-02-2019 09:37 AM
... and every ip (i.e 10.20.30.40) with 31 bits mask (255.255.255.254) is rejected.
06-11-2019 12:33 AM
Abhijeet- just got confirmed from TAC that the /31 addresses is a restriction on ALL devices running FTD due to limitations in FMC. This feature is planned implemented in a future FTD/FMC vesion. Could you share the running FTD/FMC version on your FPR2110 ?
06-12-2019 05:09 PM
Please see attached.
05-09-2021 01:57 PM
Still no support for /31 mask on interfaces in FTD 126.96.36.199. Tested on a FPR2110
Today upstream providers is consolidating IPv4-space using /31 links which prevents us from using the Firepower NGFW series as WAN/Internet edge devices.
01-24-2022 11:46 AM
Correct - not supported. There's an open ENH bugID:
12-08-2022 03:56 AM
Update - Firepower 1010
Still no support for /31 netmask on routed interfaces in FDM on the latest FTD 7.3.0 !!
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