Specifications

Configuring and Managing IP Routes
5-6 Configuring and Managing IP Interfaces and Services
Configuring and Managing IP Routes
TheIProutetablecontainsroutesthatMSSusesfordeterminingtheinterfacesforaRoamAbout
Switch’s externalcommunications.WhenyouaddanIPinterfacetoaVLANthatisup,MSS
automaticallyaddscorrespondingentriestotheIProutetable.
Fordestinationroutesthatarenotdirectlyattached,youcan
addstaticroutes.Astaticroute
specifiesthedestinationandthedefaultrouterthroughwhichtoforwardtraffic.Youcanaddthe
followingtypesofstaticroutes:
•Explicitroute—Forwardingpathfor t raffictoaspecificdestination
•Defaultroute—Forwardingpathfortraffictoadestinationwithoutanexplicitrouteinthe
routetable
A
destination canbeasubnetornetwork.Iftwostaticroutesspecifyadestination,themore
specificrouteisalwayschosen(longestprefixmatch).Forexample,ifyouhaveastaticroutewith
adestinationof10.10.1.0/24,andanotherstaticroutewithadestinationof10.10.0.0/16,thefirst
staticroute
ischosentoreach10.10.1.15,becauseithasthelongerprefixmatch.
IftheIProutetablecontainsanexplicitrouteforagivendestination,MSSusestheroute.
Otherwise,MSSusesadefaultroute.Forexample,iftheroutetabledoesnothavearoutetohost
192.168.1.10,theR o amAbout
Switchusesthedefaultroutetoforwardapacketaddressedtothat
host.EnterasysNetworksrecommendsthatyouconfigureatleastonedefaultroute.
Youcanconfigureamaximumoffourroutesperdestination.Thisincludesdefaultroutes,which
havedestination0.0.0.0/0.Eachroutetoagivendestinationmusthave a
uniquegatewayaddress.
Whentheroutetablecontainsmultipledefaultroutesormultipleexplicitroutestothesame
destination,MSSusestheroutewiththelowestmetric(costforusingtheroute).Iftwoormore
routestothesamedestinationhavethelowestcost,MSSselectsthefirstroute
intheroutetable.
MSScanusearouteonlyiftherouteisresolvedbyadirectrouteononeoftheRoamAbout
Switch’s VLANs.
Note: Before you add a static route, use the show interface command to verify that the switch has
an IP interface in the same subnet as the route’s default router. MSS requires the routes for the
interface to resolve the static route. If the switch does not have an interface in the default router’s
subnet, the static route cannot be resolved and the VLAN:Interface field of the show ip route
command output shows that the static route is down.