- If you plan to move a trunk port that is used in conjunction with filters and port monitoring, the filters and port monitoring must be reconfigured accordingly.
- After you configure a port trunk, these ports appear as a single port (labeled "Trk1") on other configuration screens, such as the Spanning Tree and Port VLAN assignment
.
- If you have switches connecting two buildings, we recommend that you pull the cable through different paths between the switches. If one link in a port trunk fails, the other ports in the same port trunk will route the traffic successfully.
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Q: If the MAC address table overflows by receiving more addresses than the switch address table can hold, how will the switch treat incoming packets whose addresses are not in table (addresses which have not been learned)?
The switch floods (broadcasts) the packet to all ports, the same as a bridge would do.
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Q: Can the Switch 2000's STP (Spanning Tree Protocol) parameters be configured from Advanced Stack Assistant (ASA)?
ASA does not allow the user to configure Spanning Tree parameters. These parameters can be changed using the switch's Console user interface.
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Q: If the Switch 2000 is set up for port mirroring, can I connect other devices to it and still use the switch for normal network use?
Yes. When a Switch 2000 port is configured for mirroring, the other ports perform normally.
The probe [mirroring] port on the Switch 2000 is not a member of any VLAN. As such, it will not appear in the "Ports VLAN Assignment" configuration screen, or any of the Spanning Tree configuration or statistics screens. The probe port, however, can send data to/from any node on any of the ports being monitored. One caveat here is that, if you attach an RMON probe to the probe port and then wish to have the RMON probe send data to a network management station, then the network management station must be attached to one of the ports being monitored. From this, you can extrapolate that end nodes on the mirroring port can communicate with end nodes on monitored ports.
NOTE: If the Automatic Broadcast Control (ABC) is configured and more than one port is monitored, then broadcast packets may be duplicated on the Monitor Port.
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Q: How many VLANs are possible on the Switch 2000?
8
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Q: What is the address table capacity of the Switch 2000?
The Switch 2000 holds 10,000 MAC addresses. There is no other per port address limit
The Switch 2000 uses a shared memory space for the address table for all ports. As such, there is no per port address limitation as was used with the Switch 16. The Switch 2000 has a 10,000 MAC address limitation. Those 10,000 addresses can come from one port or all ports on the switch.
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Q: What is the Broadcast Throttling feature on the Switch 2000?
Under "Automatic Broadcast Control" and "port configuration" there's a parameter called "broadcast limit" with values from 0 to 99, that "represents maximum percentage of broadcast/multicast words that can be transmitted".
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Switch 2000 and Switch 800t Layer 3 Switching FAQ
Q: How many RJ-45 ports come with the switch?
Four UTP port (transcievers) are shipped with the 800t. The 800t can be populated with 8 utp or 8 Fiber transceivers or any combination of the two.
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Q: What are the different types of transceivers that can be used in the switch?
The different transceivers are:
- HP J3192C Advancestack 100Base-TX UTP Transceiver
- HP J3193B Advancestack 100Base-FX Fiber-Optic Transceiver (SC)
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Switch 2000 and Switch 800t Layer 3 Switch FAQ
Q: I am redesigning my routed network with switches. How do I configure my switches so that end nodes on different subnets can communicate with each other?
There is no switch reconfiguration required. Instead, you need to configure each end node's Default Gateway to the end node's own IP address. This configuration item may be called "default gateway", or "ROUTE ADD NET", for example. Some network stacks may require other associated changes, such as setting "SUBNET MASK" to 0.0.0.0. Please consult the software stack vendor (e.g., Microsoft, FTP Software, etc.) for details.
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Q: Should I set my client PCs' Default Gateway to a switch's IP address?
No, setting a client's default gateway to a switch's IP address does not work. Remember, the switch is not a router, it doesn't know what to do with this type of packet and will drop it.
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Q: How do I set the Default Gateway to send my traffic through a router?
The answer to this question depends on your setup. Below are three setups. Choose the one that matches your network.
1) Same subnet. Two clients are on the same IP subnet (and the same physical segment). No Default Gateway configuration is needed. Each client ARPs for the other, then sends packets to the other client's MAC address.
2) Router (Simple case). Two clients are separated by the router. Each client has a gateway configured. That gateway address is the router's address (the port of the router closest to the client). When client1 on one subnet wants to communicate with client2 on the other subnet, client1 ARPs for the router, then sends all packets designated for client2 to the router's MAC address (and client2's IP address).
3) Router is multinetted. A router is multinetted when two clients are on the same physical segment, but their IP addresses are on different subnets or networks. The router port closest to these clients has two IP addresses; one address on client1's subnet, the other address is on client2's subnet. With a multinet setup, choose one of the three cases below.
3a) Each client has a gateway configured. That gateway address is the appropriate router's address (i.e., the router's address that is on the same subnet as the client.)
| Example: |
Router port is 10.10.10.10 and 11.11.11.11 |
| |
client1 is 10.10.10.50, default gateway 10.10.10.10 |
| |
client2 is 11.11.11.50, default gateway 11.11.11.11 |
When client1 wants to communicate with client2, client1 ARPs for the router (10.10.10.10), then sends all packets destined for client2 to the router's MAC address (and client2's IP address). This is the same operation as in case (2), but because both clients are on the same physical segment, the packet from client1 goes to the router, then right back out the same router port to client2. Note: this causes extra traffic: two packets on the wire instead of one, compared with (3b).
3b) Client1 has its own IP address configured as default gateway and client2 still has the router's address as gateway.
| Example: |
client1 is 10.10.10.50, default gateway 10.10.10.50 |
| |
client2 is 11.11.11.50, default gateway 11.11.11.11 |
When client1 wants to communicate with client2, client1 would expect to send the packet to the gateway. But the gateway is itself! So client1 simply ARPs for client2 (in effect, the packet came from the gateway). Client2 receives the packet, realizes that it came from a different subnet, and sends the reply to its configured gateway (the router). The router sends that packet right back out that same router port to client1 (after changing the source and destination MAC addresses). This gives us a triangular communication path:
client1--> client2--> router--> client1
3c)
Each client has its own IP address configured as a default gateway. Now the communication from client1 to client2 is a direct path, with no router involved. This is the preferred situation when combining multiple subnets or networks onto a single non-routed segment. What if the router has Proxy ARP = YES? Client1 will receive two ARP Replies, one from the router and one from client2.
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Q: How do the Switch 800t and Switch 2000 respond to proxy-ARP requests by using Layer 3 switching?
With ABC (Automatic Broadcast Control) on, the Switch 800t and Switch 2000 process ARP packets in firmware, while hardware typically handles packet forwarding. These switches store learned ARP information in an ARP table. This technical tip describes how the proxy-ARP requests are processed.
Let's review the steps the switches take to forward packets:
- Switch receives a packet.
- Switch looks up the packet's MAC source address in the address (forwarding) table.
- If the address is not in the address table, the switch firmware creates an address table entry for it.
- Switch looks up the packet's MAC destination address in the address table.
- If the address is in the table, the switch hardware forwards or discards the packet depending upon the location information in the table. If the address is not in the table, the switch forwards the packet out all ports. If the address is multicast or broadcast, the switch delivers the packet to the firmware and forwards it out all ports.
On receiving an ARP request, the Switch uses the source's IP and MAC addresses to create an ARP table entry. An ARP request contains the target's IP address, but not its MAC address, so the switch cannot construct a complete ARP table entry at this time.
The switch completes the target's ARP table entry by using these methods:
- Wait for the target to send out an ARP request (this request contains all information the ABC firmware needs to complete the ARP table entry).
- Listen for the ARP reply from the target. Note: If the reply's destination MAC address is in the address table, the switch's hardware will forward the packet and the firmware will not see the packet. Because the firmware can't see the packet, the entry cannot be completed at this time.
- The switch could send out its own ARP request for that target. Because the reply will be addressed to the switch itself, the firmware will read the packet.
Let's describe these methods in detail:
Method Number 1.
Source1 sends an ARP request for target1 and the switch does not yet have target1 in its address table. Here's the sequence of events:
- Switch receives (broadcast) ARP request.
- Switch sends that packet to the firmware. If the switch doesn't have an ARP table entry for target1's IP address, the switch creates one. This entry is incomplete, because the switch doesn't know target1's MAC address.
- Switch forwards the ARP request, unmodified (the switch's address will NOT be in the packet), out all ports except the one on which it was received.
- Switch receives unicast ARP reply from target1. Because the switch doesn't have target1's MAC address in its address table, the switch sends a "learn interrupt" to the firmware. This gives the firmware a chance to look at the packet.
- The firmware adds target1's MAC address and port # to the address table. Then it fills in target1's MAC address next to target1's IP address in the ARP table.
Method Number 2.
Source1 sends an ARP request for target1, but the switch already has target1's address in its address table. If this occurs, the following steps are executed:
- Switch receives broadcast ARP request.
- Switch sends that packet to firmware, which creates a new target1 entry in the ARP table.
- This entry is incomplete, lacking target1's MAC address.
- Switch forwards the packet, unmodified, out all ports except the one on which it was received.
- Switch receives unicast ARP reply from target1. But this time, since the switch already has target1's MAC address in its address table, there is no "learn interrupt". Instead, the hardware quickly finds the destination port and forwards the packet. The ABC firmware never sees the ARP reply. The ARP table is left with a partially-filled entry.
Method Number 3 is designed to handle Method Number 2 if it fails. That is, if the above method happens twice (that is, the switch hears two ARP requests for the same target, but the firmware doesn't see a reply), the switch will send ARP requests for that target out each port. These ARP requests are sent out three times, each with a different encapsulation:
- Ethernet II
- SNAP - with hardware type 6 (IEEE 802.3)
- SNAP - with hardware type 1 (10 Mbps Ethernet)
Because the ARP request has the switch's MAC address, the target's reply will be a unicast reply to the switch, and the firmware will see the packet and fill in the missing MAC address in the ARP table.
Note that HP routers always ARP twice: once with Ethernet II encapsulation, and once in SNAP (IEEE 802.3) format. So even though a network analyzer will show two ARP packets for the same target, this is considered only one ARP request and will not cause the switch to initiate an ARP request as described above.
Remote end nodes (separated from the switch by a router) have ARP table entries that age after two minutes. A local end node (no router separating switch from end node) has its ARP table entry flushed after five minutes from the last time the firmware sees an IP packet from that device.
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Q: How can I set the Default Gateway to point to the end node if it's using DHCP?
For an NT 4.0 DHCP server, set the Switchednetworkflag parameter. Call Microsoft support for details.
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Q: Does the switch reply to the end nodes' broadcast ARPs?
Only if Automatic Broadcast Control (ABC) is configured. Otherwise, the switch forwards the ARPs as normal traffic.
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Q: How do I configure the switch to know about the different subnet addresses and their physical locations?
There is no need to configure this. The switch learns MAC addresses automatically. Switch 2000 Ethernet Module FAQs.
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Switch 2000 Ethernet Module FAQ
Q: Can both single and multimode fiber be used on the Ethernet switch module with appropriate modules and transceivers on the Switch 2000?
The only HP-released module, the J2606A module, supports multimode only. Switch 2000 100vg Module FAQs.
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Switch 2000 100vg Module FAQs
Q: Does the J3103A 100vg module ship with two transceivers included, or do they have to be ordered separately?
For the J3103A (Switch 2000 two-port 100vg module), the transceivers must be ordered separately: These 100vg ports on a switch have three simple rules:
- CANNOT plug into an "uplink" port on a hub
- OKAY to plug into a "downlink" port on a hub
- OKAY to plug into another switch's 100vg port
The words "downlink" and "uplink" don't apply to the HP Advancestack Switch 2000. We use the words "master mode" or "end-node mode" instead.
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Q: How many 100vg modules can the Switch 2000 support?
Six, two-port 100vg modules (12 ports). Switch 2000 100Base-T Module FAQs
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Switch 2000 100Base-T Module FAQs
Q: Does the 100Base-T module ship with transceivers?
No. Transceivers need to be ordered separately so that the customer can have whatever type is desired; UTP or Fiber.
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Q: Is 10/100Mbps auto-negotiation the same as Plug-n-Play?
No. The following configuration will cause severe network problems:
The hub, switch, or router will correctly sense (not auto-negotiate) the 10Mbps or 100Mbps speed. Since the end node was configured for a specific speed and duplex state, and therefore does not negotiate, the hub, switch, or router will choose the communication mode specified by the 802.3u standard, namely half-duplex.
With one device running at half-duplex and the device on the other end of the connection at full-duplex, the connection will work reasonably well at low levels of traffic. At high levels of traffic the full-duplex device (end node, in this case) will experience an abnormally high level of CRC or alignment errors. The end users usually describe this situation as, "Performance seems to be approximately 1Mbps!". Often, end nodes will drop connections to their servers.
In this same situation, the half-duplex device will experience an abnormally high level of late collisions.
The network administrator must take care to verify the configuration of each network device during installation. Also, check the operational mode of each network device. That is, check both how you configured it and also that it comes up as you expect, for example, at 10Mbps/half-duplex.
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Switch 2000 FDDI Module FAQs
Q: What are the features of the J3108A FDDI Module for the HP Advancestack Switch 2000?
The HP Advancestack 1-port FDDI Module (J3108A) is an optional component that you can add to the HP Advancestack Switch 2000 to provide either a Dual-Attach (DAS) or a Single-Attach (SAS) connection to an FDDI ring. The FDDI Module provides a 100-Mbit/s fiber-optic port. The module can operate in any of the following ways:
- as a single dual-attach station (DAS)
- as a single-attach station connected to one or two FDDI Module single-attach stations (SAS)
- as a single-attach station connected to a concentrator
- as a dual-homed device
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Q: What are the optical characteristics of the Switch 2000's FDDI transceiver?
The HP Advancestack Switch 2000's FDDI transceiver operates at a nominal wavelength of 1300 nm. The output signal strength ranges from –19 dBm to –14 dBm, with a typical value of –16.8 dBm for 62.5/125 µm fiber.
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Switch 2000 ATM Module FAQs
Q: How does Fast Ethernet compare to ATM?
For the most part, Fast Ethernet is the clear winner on the LAN from the desktop to the backbone. Fast Ethernet at 100 Mbps and 1,000 Mbps is scalable, affordable and well-known.
ATM finds its place in LAN backbones and WANs needing these features:
- Quality of Service (QoS) capability to handle voice, video, and priorities
- Scalability from 25 Mbps to 622 Mbps
- One fabric from desktop to backbone to WAN and back.
- ATM is designed from the beginning to provide QoS. On the horizon, Fast Ethernet is now acquiring some of this functionality when accompanied by such protocols such as Layer 3 switching, IGMP, and 802.1p.
The HP J3246A ATM Uplink Module is often used to connect legacy LANs(such as Ethernet) to an existing ATM backbone.
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Q: Does the HP J3246A ATM Uplink Module work with both the "A" and "B" versions of the Switch 2000? What operating system version is required on the Switch 2000?
Yes, the ATM Uplink Module works with both the "A" and "B" version of the Switch 2000. The operating systems required are A.03.20 or later for the J3100A and B.03.02 or later for the J3100B.
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Q: What are the specifications of the ATM Module?
| Protocols |
Comments |
| LANE 1.0 |
None |
| UNI 3.0, LEC only |
ATM Switch must provide LECS, LES, and BUS. Possible 3.1 support in the future. |
| ILMI |
None |
| SONET, OC3, 62.5 um |
It is more important that an ATM switch, not an edge device, be compatible with both SONET and SDH. Up to 2 Km supported. |
|
