FRR-ISISD(8)

📦
version 10.7.1 · 23 versions
, in ubuntu stonking

💖 frr-isisd — bestie's guide to the IS-IS routing engine 💖

okay so. this is the man page for frr-isisd, aka an IS-IS routing engine for use with FRRouting. it lives in section 8 of the manual (that's the sysadmin/vibes section, iykyk). periodt. ✨

🦋 SYNOPSIS 🦋

isisd [-h] [-v]

isisd [-d|-t|-dt] [-C] [-f config-file] [-i pid-file] [-z zclient-path]
      [-u user] [-g group] [-A vty-addr] [-P vty-port] [-M module[:options]]
      [-N pathspace] [--vty_socket vty-path] [--moduledir module-path]

like. two whole ways to summon it. one is "just tell me about yourself" and the other is "okay now actually run, girl." 💅

🌸 DESCRIPTION 🌸

isisd is a routing component that works with the FRRouting routing engine. that's the whole vibe. it speaks IS-IS so your routers can all be friends and figure out the network together. 🫶

✨ OPTIONS ✨

these are the options available for the isisd command, bestie. all of them. every single one. i would never gatekeep. 👑

🎀 HELP AND VERSION 🎀

  • -h, --help — prints a short description of the daemon's command line options. little summary. a snack. 🍓
  • -v, --version — prints version and build information for the daemon.
heads up: both of these options inhibit normal operation and will immediately exit. so like, don't expect it to keep running after. it's a drive-by. 💀

💜 PROCESS CONTROL 💜

these options control background operation. aka: how does this thing exist when you're not looking at it.

  • -d, --daemon — launches the process in background/daemon mode, forking and detaching from the terminal. it's giving main character energy: it leaves the group chat and just... goes. 🌈

the parent process will delay its exit until the daemon/child has finished its initialization and has entered its main loop. this is important for zebra startup because the other daemons will attempt to connect to zebra. a return from zebra -d guarantees its readiness to accept these connections. no cap, this actually matters.

  • -t, --terminal — opens an interactive VTY session on the terminal, allowing for both state and configuration operations. note that the terminal starts operating after startup has completed and the configuration file has been loaded. (patience, babe. it's getting ready. 🧚)

the process will exit when end of file is detected on the terminal. it is possible to daemonize a process started with -t (but without -d) by sending SIGQUIT to the process (normally mapped to a ^ keypress).

the combination of --daemon (that's the -d one) and --terminal (that's -t) will delay the daemon from going into background until the terminal session ends (by end of file).

if the process receives SIGINT (e.g. a ^C keypress) in this mode, it will exit instead of daemonizing. it said no thank you to the background life. 🙈

chill note: it is safe to suspend (SIGTSTP / ^Z) the terminal session opened by the previous two options; this will only stop the terminal but not the protocol daemon itself (which runs in a separate second process.) so like, poke it awake again whenever, she's fine. 💅

🦋 CONFIGURATION AND PATHS 🦋

the following options control configuration and file system locations for frr processes:

  • -f, --config_file config-file — specify a configuration file to be used instead of the default /etc/frr/<daemon>.conf file.

note that the daemon will attempt to write to this file if the write file command is issued on its VTY interface or through vtysh. so it's not read-only, bestie. it has opinions and it will save them.

  • -C, --dryrun — load the configuration file and check its validity, then exit. vibe check, then leave. ⭐
  • -i, --pid_file pid-file — output a pid file to a location other than the default /var/run/frr/<daemon>.pid.
  • -z, --socket zclient-path — override the path of the ZAPI socket used to communicate between zebra and the various protocol daemons. the default is /var/run/frr/zserv.api. the value of this option must be the same across all daemons. fr fr, all of them. 🤝
  • -N, --pathspace pathspace — insert pathspace into all default paths, changing the defaults to:
/etc/frr/pathspace/<daemon>.conf
/var/run/frr/pathspace/<daemon>.pid
/var/run/frr/pathspace/<daemon>.vty
/var/run/frr/pathspace/zserv.api

. and / characters will not be accepted in pathspace, but the empty string will be accepted. (yes, empty. generous queen. 👑)

note that this only changes the respective defaults, it has no effect on the respective path if the -f, -i, -z or --vty_socket options are used. those ones win.

the purpose of this option is to easily group all file system related bits together for running multiple fully-separate "logical routers" on a system, particularly with Linux network namespaces. groups of daemons running with distinct pathspace values will be completely unaware of each other and not interact in any way. parallel universes. 🌌

important: this option does not do any system setup (like network namespaces.) this must be done by the user, for example by running:
ip netns exec namespace <daemon> -N namespace

🧚 PROCESS CREDENTIALS 🧚

  • -u, --user user — (default: frr)
  • -g, --group group — (default: frr)

change the user/group which the daemon will switch to.

  • -S, --skip_runas — skip setting the process effective user and group. just... don't. live your truth. 🦋
note: there is an additional group, frrvty, which controls group ownership of the VTY sockets. the name of this group cannot currently be changed, and user must be a member of this group.

💅 VTY SETUP 💅

these following options control the daemon's VTY (interactive command line) interface. the interface is available over TCP, using the telnet protocol, as well as through the vtysh frontend. two doors, same room. 🚪✨

  • -A, --vty_addr vty-addr — specify an IP/IPv6 address to bind the TCP VTY interface to. it is generally recommended to specify ::1 or 127.0.0.1. for reasons of backwards compatibility, the default is to listen on all interfaces. (not me side-eyeing that default 😭)
  • -P, --vty_port vty-port — override the daemon's default TCP VTY port (each daemon has a different default value upwards of 2600, listed below.) specifying 0 disables the TCP VTY interface.

default ports are:

zebra           2601
ripd            2602
ripngd          2603
ospfd           2604
bgpd            2605
ospf6d          2606
isisd           2608
babeld          2609
nhrpd           2610
pimd            2611
ldpd            2612
eigrpd          2613
pbrd            2615
staticd         2616
bfdd            2617
fabricd         2618
vrrpd           2619

port 2607 is used for ospfd's Opaque LSA API. (it's special. it's booked. 💅)

  • --vty_socket vty-path — overrides the directory used for the <daemon>.vty sockets. vtysh connects to these sockets in order to access each daemon's VTY. default: /var/run/frr[/<pathspace>]
NB: unlike the other options, this option specifies a directory, not a full path. don't @ me.

this option is primarily used by the SNAP packaging system, its semantics may change. it should not be necessary in most other scenarios. (iykyk. if you need it, you know. if you don't, stay out of it. 🙈)

🌟 MODULE LOADING 🌟

frr supports optional dynamically loadable modules, although these can only be loaded at startup. the set of available modules may vary across distributions and packages, and modules may be available for installation as separate packages.

  • -M, --module module[:options] — load a module named module, optionally passing options to it.

if there is a / character in module, the value is assumed to be a pathname to a module.

if there is no / character, the module directory (see next option) is searched first for a module named "<daemon>_<module>.so", then for "<module>.so". this allows for a module to exist in variations appropriate for particular daemons, e.g. zebra_snmp and bgp_snmp, with the correct one selected by -M snmp. it picks the right one for you, bestie. she's thoughtful. 🫶

the meaning of options is specific to the module being loaded. most modules currently ignore it. (so don't stress. 🙈)

modules are loaded in the order as listed on the command line. this is not generally relevant. it's just how it is.

  • --moduledir module-path — look for modules in the module-path directory instead of the default /usr/lib/frr/modules. (this path is not affected by the -N option.)
runtime tip: the list of loaded modules can be inspected at runtime with the show modules VTY command. slay. 👑

🍓 FILES 🍓

  • /usr/lib/frr/isisd — the default location of the isisd binary.
  • /etc/frr/isisd.conf — the default location of the isisd config file.
  • $(PWD)/isisd.log — if the isisd process is configured to output logs to a file, then you will find this file in the directory where you started isisd. (it follows you home. 💀)

⚠️ WARNING ⚠️

this man page is intended to be a quick reference for command line options. the definitive document is the info file frr latest or the documentation available on the project website at https://frrouting.org/. so like, don't cite this in your dissertation. 😭

🔍 DIAGNOSTICS 🔍

the daemon may log to standard output, to a VTY, to a log file, or through syslog to the system logs. FRR supports many debugging options, see the Info file, web docs or source for details. it's literally everywhere. 👀

🌈 SEE ALSO 🌈

frr-zebra(8), vtysh(1), frr-ripd(8), frr-ripngd(8), frr-ospfd(8), frr-ospf6d(8), frr-bgpd(8), frr-isisd(8), frr-babeld(8), frr-nhrpd(8), frr-pimd(8), frr-pbrd(8), frr-ldpd(8), frr-eigrpd(8), frr-staticd(8), frr-fabricd(8), frr-vrrpd(8), mtracebis(8) https://frrouting.org/

...basically the whole friend group. go say hi to all of them. 💜

🐛 BUGS 🐛

FRR eats bugs for breakfast. if you have food for the maintainers, please email dev@lists.frrouting.org. they're hungry. feed them. 🍽️✨

2017, FRR

and that's the whole page, bestie!! 🎀 this was written from the FRR source docs, version latest, dated Sep 22, 2026 — section FRR-ISISD(8) obviously. go configure some routes. you're gonna ate. 💅🦋

📦 where this page comes from