Cisco ccnp bcsi exam tutorial programs and the

Cisco CCNP/ BCSI Examination Tutorial: Broadcasts And The

Cisco CCNP/ BCSI Examination Tutorial: Broadcasts And The IP Helper-Address Command

While routers accept and create programs, they do not forward them. This can be quite a problem when a broadcast requires to get to a tool such as a DHCP or TFTP server that's on one side of a router with various other subnets beyond.

If a PC attempts to find a DNS web server with a program, the program will certainly be come by the router and will never get to the DNS server. By configuring the ip helper-address command on the router, https://www.ramseytheory.com/about-us UDP programs such as this will be translated into a unicast by the router, making the interaction feasible. The command should be set up on the interface that will be obtaining the broadcasts.

R1( config) #int e0

R1( config-if) #ip helper-address?

A.B.C.D IP location address

R1( config-if) #ip helper-address 100.1.1.2

Now, you might be questioning if this command covers all UDP services. Sorry, you're not getting off that simple! The command does ahead 8 common UDP solution broadcasts, however.

TIME, port 37

TACACS, port 49

DNS, port 53

BOOTP/DHCP Server, port 67

BOOTP/DHCP Client, port 68

TFTP, port 69

NetBIOS name solution, port 137

NetBIOS datagram service, port 138

That's going to cover most scenarios where the ip helper-address command will be useful, however what regarding those circumstances where the broadcast you need forwarded is out this listing? You can utilize the ip forward-protocol command to add any UDP port number to the list.

Additionally, to get rid of procedures from the default checklist, use the no ip forward-protocol command. In the copying, we'll add the Network Time Protocol port to the forwarding listing while getting rid of the NetBIOS ports. Bear in mind, you can make use of IOS Help to get a list of frequently filteringed system ports!

R1( config) #ip forward-protocol udp?

<0-65535> Port number

biff Biff (mail notice, comsat, 512)

bootpc Bootstrap Protocol (BOOTP) client (68 )

bootps Bootstrap Procedure (BOOTP) server (67 )

discard Discard (9 )

dnsix DNSIX safety protocol auditing (195 )

domain Domain Service (DNS, 53)

resemble Mirror (7 )

isakmp Web Safety Association and Secret Management Method (500 )

mobile-ip Mobile IP registration (434 )

nameserver IEN116 name service (outdated, 42)

netbios-dgm NetBios datagram solution (138 )

netbios-ns NetBios name service (137 )

netbios-ss NetBios session service (139 )

ntp Network Time Method (123 )

pim-auto-rp PIM Auto-RP (496 )

rip Routing Details Procedure (router, in.routed, 520)

snmp Simple Network Management Protocol (161 )

snmptrap SNMP Traps (162 )

sunrpc Sunlight Remote Procedure Telephone Call (111 )

syslog System Logger (514 )

tacacs TAC Accessibility Control System (49 )

talk Talk (517 )

tftp Unimportant Data Transfer Method (69 )

time Time (37 )

that Who solution (rwho, 513)

xdmcp X Display Manager Control Procedure (177 )