Let's use 2608/tcp for isisd.
diff --git a/redhat/quagga.spec.in b/redhat/quagga.spec.in
index 319e507..5308cc4 100644
--- a/redhat/quagga.spec.in
+++ b/redhat/quagga.spec.in
@@ -197,6 +197,7 @@
 %if %with_ospfapi
 zebra_spec_add_service ospfapi  2607/tcp "OSPF-API"
 %endif
+zebra_spec_add_service isisd    2608/tcp "ISISd vty"
 
 /sbin/chkconfig --add zebra 
 /sbin/chkconfig --add ripd