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HP 5300 Reviewer's Manual: Rapid Spanning Tree Protocol, 802.1w; Ieee 802.1d Spanning Tree Protocol

Procurve 5300xl series.
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Static IP routes: 512 maximum per chassis
IRDP (ICMP Router Discovery Protocol)
Proxy ARP
Up to 10,000 network address routes – enough for a large local environment
Up to 65,536 Layer 3 host address routes
Bootp Relay Service
Encapsulation type: Ethernet II
8 Subnets per VLAN: one primary subnet and up to 7 secondary subnets. Maximum 512 secondary subnets
per chassis. (Max 256 primary subnets (VLANs) + 512 secondary subnets = 768 max total subnets per
chassis)
DHCP relay – allows DHCP requests to be forwarded across routed interfaces to links associated with the
DHCP server
IPv4 routing, IPv6 switching: full routing of IPv4-based packets, IPv6-based packets are switched at Layer 2

2.3.2 Rapid Spanning Tree Protocol, 802.1w

Spanning Tree Protocol (STP), part of the IEEE 802.1D standard, is a Layer 2 protocol that allows
switches to be interconnected with redundant multiple links for high availability that form network
loops. In a non-spanning tree environment these loops would immediately bring the network down.
Using link cost algorithms, Spanning Tree determines which redundant links should be logically shut
down thus preventing any active network path loops.
There are two concerns with the original Spanning Tree standard, 802.1D. The first is that all redundant
links except one are not used for actual network traffic. This wastes potential bandwidth. This problem
is usually addressed by routing at the switch instead of just switching. Many network managers don't
want to do this, however, due to the higher level of management needed in a routed environment over
a Layer 2 environment. While the HP ProCurve Switch 5300xl Series can perform Layer 3 routing, there
is an easier solution in Switch Meshing, which is described in the next section.
The second concern is on link failure or loss of the STP root switch, Spanning Tree can take up to 45
seconds to re-establish network connections. In many networks a potential outage of 45 seconds is
unacceptable. While many switch vendors in the past have implemented a proprietary protocol to deal
with this, the IEEE has now established the 802.1w standard, Rapid Spanning Tree Protocol (RSTP) to
update the STP so that it responds more rapidly to link failure or loss of the root switch. Actual
recovery time is dependent (as STP is) on network complexity but can approach 1 second under
optimal conditions. RSTP is better than the proprietary protocols because it is standards based, leading
to interoperability between different switch vendors, and it provides backward compatibility with the
original STP. Sections of the network that are running under STP will recover with times associated
with STP, while those running under RSTP recover in RSTP timeframes.
2.3.2.1 IEEE 802.1D Spanning Tree Protocol
The HP ProCurve Switch 5300xl Series also support single instance spanning tree, per the 802.1D
specification. Running STP and RSTP in the same box is mutually exclusive; only one form can be run
at any given time. RSTP is the recommended configuration and can be run in the same spanning tree
domain with other switches that are running STP. STP is available, however, for users that for some
reason don't want to run RSTP.
© Hewlett-Packard Co. 2002, 2003
HP ProCurve Switch 5300xl Series Reviewer's Guide
Rev 1.1 – 2/11/2003
http://www.hp.com/go/hpprocurve
Page 14 of 35

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