Ip Interface Redundancy Protocols; Network Address Translation; Access Control Lists And Ip Access Policies - Foundry Networks Switch and Router Installation And Configuration Manual

Foundry Switch and Router Installation and Configuration Guide

IP Interface Redundancy Protocols

You can configure a Foundry Layer 3 Switch to back up an IP interface configured on another Foundry Layer 3
Switch. If the link for the backed up interface becomes unavailable, the other Layer 3 Switch can continue service
for the interface. This feature is especially useful for providing a backup to a network's default gateway.
Foundry Layer 3 Switches support the following IP interface redundancy protocols:
• Virtual Router Redundancy Protocol (VRRP) – A standard router redundancy protocol based on RFC 2338.
You can use VRRP to configure Foundry Layer 3 Switches and third-party routers to back up IP interfaces on
other Foundry Layer 3 Switches or third-party routers.
• Virtual Router Redundancy Protocol Extended (VRRPE) – A Foundry extension to standard VRRP that adds
additional features and overcomes limitations in standard VRRP. You can use VRRPE only on Foundry Layer
3 Switches.
• Foundry Standby Router Protocol (FSRP) – A Foundry router redundancy protocol developed before VRRP
and VRRPE that provides some of the features of VRRP and some of the features of VRRPE. You can use
FSRP only on Foundry Layer 3 Switches.
For configuration information, see the following:
• Virtual Router Redundancy Protocol Extended (VRRPE) – see "Configuring VRRP and VRRPE" on
page 21-1.
• Virtual Router Redundancy Protocol (VRRP) – see "Configuring VRRP and VRRPE" on page 21-1.
• Foundry Standby Router Protocol (FSRP) – see "Configuring FSRP" on page 22-1

Network Address Translation

Foundry's chassis Layer 3 Switches support Network Address Translation (NAT). NAT enables private IP
networks that use nonregistered IP addresses to connect to the Internet. Configure NAT on a Foundry Layer 3
Switch that is placed at the border of an inside network and an outside network (such as the Internet). NAT
translates the internal local addresses to globally unique IP addresses before sending packets to the outside
network.
For configuration information, see "Network Address Translation" on page 20-1.

Access Control Lists and IP Access Policies

Foundry Layer 3 Switches provide two mechanisms for filtering IP traffic:
• Access Control Lists (ACLs)
• IP access policies
Both methods allow you to filter packets based on Layer 3 and Layer 4 source and destination information.
ACLs also provide great flexibility by providing the input to various other filtering mechanisms such as route maps,
which are used by BGP4. ACLs also provide the input for Policy-Based Routing (PBR), which allows you to
selectively modify and route IP packets based on their source IP address.
IP access policies allow you to configure QoS based on sessions (Layer 4 traffic flows).
Only one of these filtering mechanisms can be enabled on a Foundry device at a time. Foundry devices can store
forwarding information for both methods of filtering in the session table.
For configuration information, see the following:
• "Using Access Control Lists (ACLs)" on page 13-1
• "Policies and Filters" on page C-1
15 - 8 December 2000