Leaflet

OL-11615-01

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/fun_r/cfr

_1g03.htm#wp1031545

For more information about AutoInstall, refer to the following URL:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide

_chapter09186a00800ca735.html

IP Source Routing

The IP protocol supports source routing options that allow the sender of an IP packet to control the route

that the datagram will take toward its ultimate destination, and generally the route that any reply will

take. These options are rarely used for legitimate purposes in real networks. Some older IP

implementations do not process source-routed packets properly, and it might be possible to crash

machines running these implementations by sending them datagrams with source routing options. By

default Cisco IOS software forwards IP packets with source routing header options. As a general best

practice, IP source routing should be disabled unless strictly necessary. To have the software discard any

IP packet containing a source-route option, use the no ip source-route global configuration command

as shown in the following example:

Router(config)# no ip source-route

For more information about the ip source-route command, refer to the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/ipras_r/ip1

_i2g.htm#wp1081830

PAD

Cisco IOS software provides a PAD (packet assembler/disassembler) service that allows simple devices

such as character-mode terminals to connect to legacy X.25 networks. With this service, Cisco IOS

software devices and other X.25 network equipment can establish PAD sessions. By default, the PAD

service is enabled on Cisco IOS software, but it could be used to gain unauthorized or inappropriate

access. Therefore, unless needed, this service should be disabled using the no service pad global

configuration command, as shown in the following example:

Router(config)# no service pad

For more information about the PAD service refer to the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/wan_r/wan

_s1g.htm#wp1032441

Proxy ARP

Proxy Address Resolution Protocol (ARP), as defined in RFC 1027, is a technique that helps machines

on a subnet reach remote subnets without configuring routing or a default gateway. Proxy ARP is

typically implemented on routers, and when configured, the router answers all ARP requests on the local

subnet on behalf of systems some hops away.

In this model, local hosts send ARP requests for each destination for which they do not have any routing

information, and the router replies with its own MAC address as the next hop. By default, Cisco IOS

software implements proxy ARP on all interfaces. However, unless it is specifically needed, it should be

disabled using the no ip proxy-arp interface configuration command, as shown in the following

example:

Router(config-if)# no ip proxy-arp