Troubleshooting a network connectivity issue is quite challenging in a complex Data Center Network with live production traffic.
Below are few basic methods to identify a node in the traffic path that drops packets which would cause network connectivity issues. This procedure is in general and not related to any specific vendor as troubleshooting options varies with each vendor.
Let’s consider below simple topology for troubleshooting purpose:
R1(IP:220.127.116.11)— R2 — R3 — R4(IP:18.104.22.168)
Problem statement#1: 100% ping loss between R1 and R4. In this case, ping from R1 to R4’s interface IP fails 100%. Continue reading
In this article, I will be discussing about two different modes that an FCF switch can operate in FCoE topology.
FCF(FCoE Forwarder) is a switch that supports both Ethernet(FCoE) functionality like FIP, DCBx, LAN protocols and FC(Fiber Channel) functionality like fabric login, zoning and name services. FCF connects the CNA on the server end to any storage array(Native FC), by bridging the gap between Ethernet LAN and storage . Dell S5000 is an example of FCF switch which can be configured in two different modes- NPG or Full Fabric mode. Continue reading
Following are most common port names used in FC/FCoE Technology:
- Ports on end host(i:e HBA) and storage array(target port) are called as N_port in FC topology.
- Called as VN_port in FCoE terminology.
- HBA’s that handles IP traffic are called as CNA in FCoE terminology.
- Each N-port will have a unique WWPN (64 bit) assigned by vendor. We use this WWPN while configuring Zoning on FC switch.
- Fabric Provided Mac Address (FPMA) is a 48-bit mac-address that uniquely identifies a single VN_port(CNA) on an Enode. FPMA is assigned to an VN_port by FC switch during FLOGI process.
- FPMA (48-bit mac) = FC-map (24 bits) + FC_ID (24 bits)
- FC-MAP: 24 bit value that identifies the FC switch. Default value: 0efc00
- FC_ID: Also called as N_port ID. A 24-bit value assigned to a VN_Port by the FC switch to uniquely identify it in the local fabric network.
- So, there will be one-one mapping between physical N-port WWPN and FPMA/N_port ID in a fabric network.
Posted in FCOE
Tagged Expansion Port, e_node, e_port, FC topology, fcoe, FCoE terminology, fpma, f_port, n_port, n_port ID, VN_port ID, WWPN
This article is about how to configure FCoE functionality on Qlogic CNA card-QL8262 installed on a Dell PowerEdge R720 server running ESXi 5.5.
QL8262 is dual port CNA card that supports LAN, iSCSI and FCoE. Configuring Qlogic FCoE card on an ESXi host is a two-step process;
- Install driver on ESXi so that it can detect Qlogic cards.
- Enable FCoE functionality on Qlogic CNA.
Snake test is usually performed to check whether a device can handle traffic Tx/Rx to/from all active interfaces at line-rate. The snake test is usually performed as below;
Traffic SENDER—- 0/1(Router)0/2 —- 0/3(same router)0/4—-0/5(same router)0/6— Traffic RECEIVER
ports 0/1-2 are untagged(access ports) in a vlan; say vlan2
ports 0/3-4 are untagged(access ports) in a vlan; say vlan3
ports 0/5-6 are untagged(access ports) in a vlan; say vlan4
So, packets sent by the SENDER at line-rate will be received at the RECEIVER. Same can be done vice-versa. ie: line-rate traffic from RECEIVE to SENDER. Continue reading
When a router receives a packet, it would check the routing table to forward the packet to the egress(outgoing) interface based on the destination IP address. If we need to forward packet based on other field, like source IP etc, we need to use PBR rules to override the routing table entry. The issue is, after configuration PBR, the packets are not routed to the firewall as in the PBR rule rather forwarded based on the routing table.
- PBR was configured to route packets to a firewall instead of taking the normal route as in Routing table. Continue reading
VNC is used to display X windows session running on a remote server. For network engineers, it is really useful to have Konsole/xterm session running on a Linux server connecting to network devices. Whenever we need access to the switches/routers, we can just login to VNC server using a VNC client. All sessions will be active (unless idle timeout is configured on switches/routers) and ready to use.
Steps to install VNCserver in Linux: Continue reading