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Cisco CCNP / BCSI Examination Tutorial: Broadcasts And also theCisco CCNP / BCSI Exam Tutorial: Broadcasts Along with the IP Helper-Tackle CommandWhile routers take and create broadcasts, they don't ahead them. This can be really a difficulty each time a broadcast really should get to a tool like a DHCP or TFTP server that’s on a person side of a router with other subnets on one other side. If a Computer makes an attempt to Track down a DNS server which has a broadcast, the published will be stopped because of the router and won't ever get on the DNS server. By configuring the ip helper-deal with command to the router, UDP broadcasts which include this will be translated into a unicast from the router, building the interaction feasible. The command should be configured over the interface that will be obtaining the broadcasts.R1(config)#int e0R1(config-if)#ip helper-address ? A.B.C.D IP spot deal withR1(config-if)#ip helper-deal with one hundred.one.1.twoNow, you might be wondering if this command handles all UDP products and services. Sorry, you’re not getting off that effortless! The command does forward eight prevalent UDP provider broadcasts, though. TIME, port 37TACACS, port forty nineDNS, port fifty threeBOOTP/DHCP Server, port sixty sevenBOOTP/DHCP Customer, port sixty eightTFTP, port sixty nineNetBIOS title company, port 137NetBIOS datagram service, port 138That’s likely to address most scenarios where the ip helper-tackle command will probably be valuable, but what about All those conditions wherever the published you need forwarded is not on this listing? You should utilize the ip forward-protocol command so as to add any UDP port variety to the record.Additionally, to remove protocols in the default record, make use of the no ip ahead-protocol command. In the subsequent instance, we’ll add the Network Time Protocol port to the forwarding list even though eliminating the NetBIOS ports. Keep in mind, You may use IOS Assist to receive a list of usually filtered ports!R1(config)#ip forward-protocol udp ? <0-65535> Port selection biff Biff (mail notification, comsat, 512) bootpc Bootstrap Protocol (BOOTP) consumer (68) bootps Bootstrap Protocol (BOOTP) server (67) discard Discard (nine) dnsix DNSIX stability protocol auditing (195) domain Domain Identify Services (DNS, 53) echo Echo (seven) isakmp Net Security Affiliation and Key Administration Protocol (five hundred) cellular-ip Cell IP registration (434) nameserver IEN116 name assistance (out of date, 42) netbios-dgm NetBios datagram provider (138) netbios-ns NetBios identify fast services (137) netbios-ss NetBios session company (139) ntp Community Time Protocol (123) pim-auto-rp PIM Vehicle-RP (496) rip Routing Information and facts Protocol (router, in.routed, 520) snmp Uncomplicated Community Management Protocol (161) snmptrap SNMP Traps (162) sunrpc Sunlight Remote Procedure Simply call (111) syslog Method Logger (514) tacacs TAC Entry Management Technique (49) communicate Converse (517) tftp Trivial File Transfer Protocol (sixty nine) time Time (37) who Who provider (rwho, 513) xdmcp X Show Supervisor Command Protocol (177