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LANE server redundancy support through simple server redundancy protocol (SSRP)
IP gateway redundancy support using hot standby routing protocol (HSRP)
DECnet, Banyan VINES, and XNS routed protocols
1. Addressing
LANE requires MAC addressing for every client. LANE clients defined on the same interface or
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subinterface automatically have the same MAC address. This MAC address is used as the end system
identifier (ESI) value of the ATM address. Though the MAC address is duplicated the resulting ATM
address representing each LANE client is unique. All ATM addresses must be unique for proper ATM
operations. Each LANE services component has an ATM address unique form all other ATM addresses.
2. LANE ATM Addresses
LANE uses the NSAP ATM address syntax however it is not a Layer 3 network address. The address format used by LANE
is :
A 13-byte prefix that includes the following fields defined by the ATM Forum:
AFI (Authority and Format Identifier) field (1 byte)
DCC (Data Country Code) or ICD (International Code Designator) field (2 bytes)
DFI field (Domain Specific Part Format Identifier) (1 byte)
Administrative Authority field (3 bytes)
Reserved field (2 bytes)
Routing Domain field (2 bytes)
Area field (2 bytes)
A 6-byte end-system identifier (ESI)
A 1-byte selector field
1. Cisco's Method of Automatically Assigning ATM Addresses
The Cisco IOS supports an automated function of defining ATM and MAC addresses. Theses addresses are used in the
LECS database. The automation process uses a pool of eight MAC address that are assigned to each router ATM interface.
The Cisco IOS applies the addresses to the LANE components using the following methodology:
All LANE components on the router use the same prefix value. The prefix value identifies a switch and must be
defined within the switch.
The first address in the MAC address pool becomes the ESI field value for every LANE client on the interface.
The second address in the MAC address pool becomes the ESI field value for every LANE server on the interface.
The third address in the MAC address pool becomes the ESI field value for the LANE broadcast-and-unknown server
on the interface.
The fourth address in the MAC address pool becomes the ESI field value for the LANE configuration server on the
interface.
The selector field for the LANE configuration server is set to a 0 value. All other components use the subinterface
number of interface to which they are defined as the selector field.
The requirement that the LANE components be defined on different subinterfaces of an ATM interface results in a unique
ATM address due to the use of the selector field value being set to the subinterface number.
1. Using ATM Address Templates
ATM address definitions is greatly simplified through the use of address templates. However, these
templates are not supported for the E.164 ATM address format. The address templates used for LANE
ATM addressing can use either an asterisk (*) or an ellipsis (& ) character. An asterisk is used for
matching any single character. An ellipsis is used for matching leading or trailing characters. Table 6.1
lists the address template value determination.
Unspecified Digits In Resulting Value Is
Prefix (first 13 bytes) Obtained from ATM switch via Interim Local
Management Interface (ILMI)
ESI (next 6 bytes) Filled using the first MAC address of the MAC
address pool plus
0-LANE client
1-LANE server
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2-LANE broadcast-and-unknown
server
3-LANE Configuration server
Selector field (last 1 byte) Subinterface number, in the range 0 through 255.
The ATM address templates can be either a prefix, or ESI template. When using a prefix template, the
first 13 bytes match the defined prefix for the switch but uses wildcards for the ESI and selector fields.
An ESI template matches the ESI field but uses wildcards for the prefix and selector fields.
2. Rules for Assigning Components to Interfaces and Subinterfaces
The LANE components can be assigned to the primary ATM interface as well as the subinterfaces. The following are
gudielines for applying LANE components on a Cisco router ATM interface.
The LECS always runs on the primary interface.
Assignment a component to the primary interface falls through to assigning that component on the 0 subinterface.
The LES and LEC of the same emulated LAN can be configured on the same subinterface in a router.
LECs of two different emulated LANs must be defined on a different subinterface in a router.
LESs of two different emulated LANs must be defined on a different subinterface in a router.
1. Redundancy in LANE environments
The ATM LANE V 1.0 specification does not provide for redundancy of the LANE components. High avialbility is always
a goal for network designers and the single point of failure in the LANE specification requires a technique for redundancy.
Cisco IOS supports LANE redundancy through the implmenentation of Simple Server Replicatoin Protocol (SSRP).
SSRP supports redundancy for LECS and LES/BUS services. LECS redundancy is provided by configuring multiple LECS
address in the ATM switches. Each defined LECS is defined with a rank. The rank is the index (number of the entry in the
LECS address table) of the LECS address in the table. At iitialization the LECS requests the LECS address table form the
ATM swixth. The requesting LECs onreceipt of the LECS addres table tries to connect to all the LECSs with a lower rank.
In this way the LECS learns of its role in the redundancy hierarchy. A LECS that connects with a LECS whose rank is
higher places itself in a backup mode. The LECS that connects to all other LECS and does not find a ranking higher than its
own assumes the responsibility of the primary LECS. In this hierarchy, as shown in Figure 6.2, the failure of a primary
LECS does not result in a LANE failure. Rather , the second highest ranking LECS assumes the primary LECS role. Loss of
the VCC between the primary and highest ranking secondary signals the highest secondary ranking LECS that it is now the
primary LECS.
In theory any number of LECS can be designed using SSRP. However, Cisco recommends that no more than three LECS be
designed into SSRP. The recommendation is based on adding a degree of complexity to the network design which can lead
to an increase in the time it takes for resolving problems.
LES/BUS redundancy using SSRP is similar in that it uses a primary-secondary hierarchy however, the primary LES/BUS
pair is assigned by the primary LECS. The LECS determines the primary LES/BUS pair by determining the LES/BUS pair
having the highest priority with an open VCC to the primary LECS. The LES/BUS pair priority is assigned during
configuration into the LECS database.
The following guidelines are highly recommended for desinging the LECS redundancy scheme and ensuring a properly
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