Configuring Routes and Monitoring IP Traffic
7-16 Configuring IP
Usethis“no”formofthecommandtoremoveaUDPportorprotocol,disablingforwardingfor
theassociatedservice:
no ip forward-protocol {udp [port | protocol]}
Enabling DHCP/BOOTP Relay
DHCP/BOOTPrelayfunctionalityisappliedwiththehelpofIPbroadcastforwarding.Atypical
situationoccurswhenahostrequestsanIPaddresswithnoDHCPserverlocatedonthatsegment.
AroutingmodulecanforwardtheDHCPrequesttoaserverlocatedonanothernetworkif:
•IPforward‐protocolis
enabledforUDPasdescribedintheprevioussection,and
•theaddressoftheDHCPserverisconfiguredasahelperaddressonthereceivinginterfaceof
theroutingmoduleforwardingtherequest,asdescribedinthefollowingsection.
TheDHCP/BOOTPrelayfunctionwilldetecttheDHCPrequestandmakethe
necessarychanges
totheheader,replacingthedestinationaddresswiththeaddressoftheserver,andthesourcewith
itsownaddress,andsendittotheserver.Whentheresponsecomesfromtheserver,theDHCP/
BOOTPrelayfunctionsendsittothehost.
Frominterfaceconfigurationmode,usethiscommand
toenableDHCP/BOOTPrelay,andthe
forwardingoflocalUDPbroadcaststooneormorespecificdestinationaddresses.
ip helper-address address
Example
ThisexampleshowshowtopermittopermitUDPbroadcastsfromhostsonnetworks
191.168.1.255and192.24.1.255 toreachserversonthosenetworks:
Configuring Routes and Monitoring IP Traffic
UsetheproceduresinthissectiontoperformthefollowingIProuteconfigurationandtraffic
monitoringtasks:
• AddingorRemovingStaticIPRoutes
• DisplayingIPTrafficandPerformance
• ClearingIPTrafficCounters
Note: If a particular service exists inside the node, and there is no need to forward the
request to remote networks, the “no” form of this command should be used to disable the
forwarding for the specific port. Such requests will not be automatically blocked from
being forwarded, just because a service for them exists in the node.
Matrix>Router(config)#ip forward-protocol udp
Matrix>Router(config)#interface vlan 1
Matrix>Router(config-if(Vlan 1))#ip helper-address 192.168.1.255
Matrix>Router(config)#interface vlan 2
Matrix>Router(config-if(Vlan 2))#ip helper-address 192.24.1.255
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