Source: netcfg
Version: 1.187
Severity: normal

Dear Maintainer,

Setting a netmask of (in my case using preseed, but I guess the 
same happens if using the UI)
fails the installer with Unreachable gateway (even if the gateway is set).
I agree it can be seen as an odd setup, but it's valid and works when 
configured manually in busybox and Linux.
My usecase is creating routed Debian VMs, where the host have a static route to 
the guest's IP (or v6 /128).
With a smaller subnet (like /23), we would have to use proxy ARP which is 
usually not recommended.

You can see more information in:

My current workaround is to use a smaller netmask then run the following in 
IFACE=$(ip -4 route list 0/0 | sed -r 's/.*dev ([^ ]*) .*/\1/' | head -1)
IP="$(ip address show dev $IFACE | egrep '^[[:space:]]+inet ' | cut -d ' ' -f 6 
| cut -d '/' -f 1)"
ip addr del $IP dev $IFACE
ip addr add $IP/32 dev $IFACE
ip route add dev $IFACE scope link
ip route add default via

Right after "netcfg"
It would of course be cleaner if netcfg were to handle a /32 "out of the box".

Similarly, DHCP can allocate such IPs, see for example :
I haven't tested DHCP in Debian Installer with such setup though.

Please let me know if I can be of any help.


-- System Information:
Debian Release: 12.5
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 
'stable-debug'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 6.1.0-18-amd64 (SMP w/1 CPU thread; PREEMPT)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)

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