Tag - packet

Virtual Local Area Network (VLAN)

Virtual Local Area Network (VLAN)

Virtual Local Area Network (VLAN) is a logical grouping of hosts. This grouping allows them to communicate if they are on the same LAN, irrespective of the physical topology of the network. VLAN offer the ability to group computers together into logical workgroups. This can simplify network administration when connecting clients to servers that are geographically distributed. Typically, VLAN consist of co-workers in the same department but in different locations or a cross functional team working on a joint endeavor.

Virtual Area Network (VLAN)

 

Virtual Local Area Network (VLAN)

Virtual Local Area Network (VLAN) is a logical grouping of hosts. This grouping allows them to communicate if they are on the same LAN, irrespective of the physical topology of the network. VLAN offer the ability to group computers together into logical workgroups. This can simplify network administration when connecting clients to servers that are geographically distributed. Typically, VLAN consist of co-workers in the same department but in different locations or a cross functional team working on a joint endeavor.

 

VLAN Types:

There are two basic types of VLAN:

  1. Tagged: VLAN is based on the IEEE 802.1Q specification. Each packet has a 4-byte tag added to the packet hearer. The switch must support IEEE 802.1Q tagging and be properly configured. Please check your switch documents for the correct switch configuration.
  2. Un-tagged: Or Port-based VLANs are statically configured on the switch. They are transparent to connected devices.

 

Execution Reviews:

  • Many companies software supports maximum of 64 VLANs per network port or team.
  • To set up IEEE VLAN membership (Multiple VLANs), the adapter must be attached to a switch with IEEE 802.1Q VLAN capability.
  • VLAN can co-exist with teams (if the adapter supports both). The team must be defined first, then you can set up your VLAN.
  • You can set up only one untagged VLAN per port or team. You must have at least one tagged VLAN before you can set up an un-tagged VLAN.
  • After creating the VLAN, the adapter associated with the VLAN can have a temporary loss of connectivity.
  • A VLAN cannot be removed if a virtual NIC is bound to it.
  • If VLAN is assigned to an adapter, the Priority and VLAN option on the Advanced properties tab is enabled and cannot be disabled until all VLAN is removed from the adapter.
  • If you change the setting under the Advanced tab for one VLAN, it changes the settings for all VLANS using that port.
  • Advanced Networking Services (ANS) VLANs are not supported on adapters and teams that have VMQ enabled. But, VLAN filtering with VMQ is supported via Microsoft Hyper-V VLAN interface.
  • You can have different VLAN tags on a child partition and its parent. Those settings are separate from one to another, and can be different or the same. The VLAN tag on the parent and child must be the same if you want the parent and child partitions to be able to communicate through that VLAN.

For more information see Microsoft Hyper-V virtual NIC on teams and VLANs.

 

Advantages of VLAN:

  • Improve LAN configuration updates (Adding, Editing, Moves).
  • Improve network performance.
  • Simplicity in your management tasks.
  • Frontier for broadcast storms.
  • Reduce security complications.

 

Before Patch Installation:

 Before Patch Installation (VLAN)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After Patch Installation:

After Patch Installation (VLAN)

BGP Adjacency States

BGP Adjacency States

  1. Idle State
  2. Connect State
  3. Active State
  4. OpenSent State
  5. OpenConfirm State
  6. Established State

1. Idle State:

Idle is the initial state of a BGP connection. The BGP speaker is waiting for a start event, generally either the establishment of a TCP connection or the re-establishment of a previous connection. Once the connection is established, BGP moves to the next state.

Attributes

  • Refuse all incoming BGP connections
  • Start the initialization of event triggers
  • Initiates a TCP connection with its configured BGP peer
  • Listens for a TCP connection from its peer
  • Changes its state to Connect

If an error occurs at any state of the FSM process, the BGP session is terminated immediately and returned to the Idle state. Some of the reasons why a router does not progress from the Idle state are:

  • TCP port 179 is not open
  • A random TCP port over 1023 is not open
  • Peer address configured incorrectly on either router
  • AS number configured incorrectly on either router

2. Connect State:

Connect is the next state of a BGP connection. If the TCP connection complvces, BGP will move to the OpenSent stage if the connection does not complvce, BGP goes to Active.

Attributes

  • Waits for successful TCP negotiation with peer
  • BGP does not spend much time in this state if the TCP session has been successfully established
  • Sends Open message to peer and changes state to OpenSent

If an error occurs, BGP moves to the Active state. Some reasons for the error are:

  • TCP port 179 is not open
  • A random TCP port over 1023 is not open
  • Peer address configured incorrectly on either router
  • AS number configured incorrectly on either router

3. Active State:

Active indicates that the BGP speaker is continuing to create a peer relationship with the remote router. If this is successful, the BGP state goes to OpenSent. You’ll occasionally see a BGP connection flap between Active and Connect. This indicates an issue with the physical cable itself, or with the configuration.

Attributes

  • If the router was unable to establish a successful TCP session, then it ends up in the Active state
  • BGP FSM tries to restart another TCP session with the peer and, if successful, then it sends an Open message to the peer
  • If it is unsuccessful again, the FSM is reset to the Idle state

Repeated failures may result in a router cycling between the Idle and Active states. Some of the reasons for this include:

  • TCP port 179 is not open
  • A random TCP port over 1023 is not open
  • BGP configuration error
  • Network congestion
  • Flapping network interface

4. OpenSent State:

OpenSent indicates that the BGP speaker has received an Open message from the peer. BGP will dvcermine whether the peer is in the same AS (iBGP) or a different AS (eBGP) in this state.

Attributes

  • BGP FSM listens for an Open message from its peer
  • Once the message has been received, the router checks the validity of the Open message
  • If there is an error it is because one of the fields in the Open message doesn’t match between the peers, e.g., BGP version mismatch, MD5 password mismatch, the peering router expects a different My AS, etc. The router then sends a Notification message to the peer indicating why the error occurred
  • If there is no error, a Keepalive message is sent, various timers are set and the state is changed to OpenConfirm

5. OpenConfirm State:

In OpenConfirm state, the BGP speaker is waiting for a keepalive message. If one is received, the state moves to Established, and the neighbor relationship is complvce. It is in the Established state that update packets are actually exchanged.

Attributes

  • The peer is listening for a Keepalive message from its peer
  • If a Keepalive message is received and no timer has expired before reception of the Keepalive, BGP transitions to the Established state
  • If a timer expires before a Keepalive message is received, or if an error condition occurs, the router transitions back to the Idle state

6. Established State:

In Established state, if one of keepalive message is received, the state moves to Established, and the neighbor relationship is complvce. It is in the Established state that update packets are actually exchanged.

Attributes

  • In this state, the peers send update messages to exchange information about each route being advertised to the BGP peer
  • If there is any error in the update message then a Notification message is sent to the peer, and BGP transitions back to the idle state
  • If a timer expires before a Keepalive message is received, or if an error condition occurs, the router transitions back to the Idle state

BGP-Adjacency-States

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