switching.md 2.1 KB
title: Switching breadcrumbs:
- title: Configuration
- title: Network --- {% include header.md %}
Layer 2 stuff.
Terms
| Cisco IOS | Brocade ICX | | - | - | | Access port | Untagged port | | Trunk port | Tagged port | | Native VLAN | Dual mode |
VLAN IDs
Valid VID range (802.1Q): 1-4095
Reserved:
- 1: Default native VLAN.
- 1002: FDDI default (Cisco).
- 1003: Token ring default (Cisco).
- 1004: FDDI-Net (Cisco).
- 1005: TRNET (Cisco).
- 4095: Implementation use.
Spanning Tree Protocol (STP)
Variants
| Names | Supporting Devices* | Description |
|---|---|---|
| 802.1D, STP | Cisco IOS, Linksys LGS | Single instance, slow |
| PVST/PVST+ | Cisco IOS | Like STP, one instance per VLAN |
| VSTP | Juniper | Compatible with Cisco's PVST |
| 802.1w, RSTP | Brocade ICX, Linksys LGS | Single instance, fast, backwards-compatible with STP. |
| Rapid-PVST+ | Cisco IOS | Like PVST+ but based on RSTP |
| VSTP | Juniper | Based on RSTP, compatible with STP and Cisco's PVST |
| 802.1s, MSTP, MST | Cisco IOS | Multiple instances with configurable VLAN members |
| 802.1Q | ??? |
(*) Very incomplete list.
Notes
- Use extended system ID for multi-VLAN switches.
- Make sure all switches are using compatible variants and default priorities.
- Make sure all VLANs are running STP or that STP is running globally (not per VLAN).
- STP (excluding per-VLAN STP and generally not MST) (including rapid versions) will consider multiple links between switches a loop, even when the links carry different VLANs.
- The bridge priority should generally be a multiple of 4096.
- PVST and 802.1Q regions cannot interoperate directly, but can through PVST+ regions.
Cisco IOS
- VTP can be very dangerous if not used properly and is enabled by default. It also doesn't carry MST configuration.
- Rapid-PVST+ ignores UplinkFast and BackboneFast and supports UDLD.
Inter-Model Compatibility Examples
Example 1
TODO I have not actually tested this properly.
- Cisco IOS (Cat 3750G):
rapid-pvst - Brocade (ICX 6610):
802.1w - Linksys (LGS326):
stp(slow but works) - Use the same default priority, e.g. 32768.
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