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Configuring ISG Port-Bundle Host Key

Prerequisites for the ISG Port-Bundle Host Key Feature

For information about release and platform requirements, see the “Feature Information for ISG

Port-Bundle Host Key” section on page 9.

The external portal must support port-bundle host keys and must be configured with the same

port-bundle host key parameters.

Restrictions for the ISG Port-Bundle Host Key Feature

The following restrictions apply to the ISG Port-Bundle Host Key feature:

• The ISG Port-Bundle Host Key feature must be separately enabled at the portal and at all connected

ISGs.

• All ISG source IP addresses configured with the source command must be routable in the

management network where the portal resides.

• For each portal server, all connected ISGs must have the same port-bundle length.

• The ISG Port-Bundle Host Key feature uses TCP. Packets will not be mapped for a subscriber who

is not sending TCP traffic.

• Specifying the Port-Bundle Host Key feature in a user profile will work only when the user profile

is available prior to the arrival of IP packets; for example, for PPP sessions or for DHCP-initiated

IP sessions with transparent autologon.

Information About ISG Port-Bundle Host Key

Before you configure the ISG Port-Bundle Host Key feature, you should understand the following

concepts:

• Overview of ISG Port-Bundle Host Key, page 2

• Port-Bundle Host Key Mechanism, page 2

• Benefits of ISG Port-Bundle Host Key, page 3

Overview of ISG Port-Bundle Host Key

The ISG Port-Bundle Host Key feature serves as an in-band signaling mechanism for session

identification at external portals. TCP packets from subscribers are mapped to a local IP address for the

ISG gateway and a range of ports. This mapping allows the portal to identify the ISG gateway from

which the session originated. The mapping also identifies sessions uniquely even when subscribers have

overlapping IP addresses. The ISG Port-Bundle Host Key feature enables a single portal to be deployed

for multiple VRFs even when there are subscribers with overlapping IP addresses.

Port-Bundle Host Key Mechanism

With the ISG Port-Bundle Host Key feature, an ISG performs Port-Address Translation (PAT) and

Network Address Translation (NAT) on the TCP traffic between the subscriber and the portal. When a

subscriber TCP connection is set up, the ISG creates a port mapping that changes the source IP address

Cisco IOS XE Intelligent Services User Manual

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