Download WinBox and connect to Mikrotik. Select “IP” – > “Firewall”. Select NAT. Click on plus and select “Chain” -> “dsnat”. Enter dst.address – this is tipically public IP address of Mikrotik router. Enter protocol type (for HTTP this is “tcp”). Enter dst.port – port, what will be NAT-ed. Click “Atcion” tab. Select “Action” -> […]
Category: Network concepts
Upgrade OS on NEXUS switch from v6 to v9
There is no option to direct upgrade from v6 to v9. Following steps allow this happens. Remember memory limits and use smaller image, if you need to. Copy new image to switch. Install image. remove old image Install v7 image. delete old images Copy v9 image do some configuration change Install v9.
Port-channel (PC) / Virtual port-channel (VPC)
Port-Channel – is a bundle of 2+ links between 2 switches (see example below). Links bundled together and connection utilize throughput of both links. In comparison to spanning tree, links utilization become more efficient, as both links are used for data transfer. Sample configuration. Sw1 Sw2 Virtual Port-Channel – same as Port-Channel, with single difference […]
CDP / LLDP
CDP (Cisco Discovery Protocol) / LLDP (Link Layer Discovery Protocol) – protocols, allowing network devices to announce they presence to other devices. CDP – Cisco proprietary protocol, therefore it is working only with Cisco devices. LLDP – open protocol. Usage examples Best practice / configuration examples CDP enabled by default on all cisco devices. Best […]
HSRP / FHRP
HSRP (Hot Standby Routing Protocol) – Cisco proprietary protocol used for first hop redundancy. FHRP (First Hop Redundancy Protocol) – open protocol for same goal: first hop redundancy. 2 switches required for implementation. HSRP using virtual MAC and virtual IP to process packets. (And yes, in our case it is working on VLAN interfaces). Sample […]
What is VRF?
VRF – Virtual Routing and Forwarding. Basically it is virtual router within physical router. With separated configuration and routing tables/databases. To use VRF, interface(or subinterface) should be assigned to VRF. Sample configuration. Basic VRF configuration: Add interface to VRF: Static route for VRF: Configure Dynamic routing for VRF (OSPF as example):
What is SVI?
SVI – Switched Virtual Interface. Virtual interface on Cisco device, that connects and route traffic between devices in a VLAN. It allows switch to communicate with other devices in VLAN, such as computers or servers and allow routing between them and external networks (with some extra configuration of switch). Sample configuration:
Switchport access/trunk mode
Two most useful modes at which ports on switch can work is ‘access’ and ‘trunk’ mode. Access mode – all incoming traffic tagged with VLAN tag by switch and processed further. Outgoing traffic for this port processed only for associated VLAN. Trunk mode – allows VLAN/tagged incoming traffic and sort out incoming traffic basing on […]
What is MTU, why do we need to have same MTU values on both sides of link and how to troubleshoot issues with MTU.
MTU in networks is Maximum Transmission Unit. And basically, it indicates the maximum size of packet what could be processed by network device without fragmentation. The default MTU is 1500, therefore, all packets what is bigger than 1500 bytes, should be fragmented to successfully transferred by network devices. Misconfiguration of MTU on different sides of […]