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A networker's blog

DHCP Relay on EX9200

In this post we will see how DHCP Relay is configured on EX9200. Actually, the same type of configuration can be applied on any Juniper platform that supports ELS. DHCP Relay allows clients to get an IP address even when they are not in the same broadcast domain with the DHCP server. The DHCP Relay… Keep reading »

OpenNMS to monitor Juniper, Cisco and Linux devices

This post will be about OpenNMS and what it can do to monitor the network. OpenNMS is similar to LibreNMS covered here. The installation is pretty straighforward and installation steps for various OSs are provided. The official documentation containing installation steps, tutorials, links to community is on OpenNMS wiki. But let’s see how this looks… Keep reading »

LibreNMS to monitor Juniper, Cisco and Linux devices

This post will be about LibreNMS and what it can do for you. LibreNMS is an open-source network monitoring tool and it is a fork of Observium. LibreNMS provides graphs, notifications to allow you to monitor the network and be informed of any changes taking place. The documentation is pretty exhaustive and you can get… Keep reading »

Running a shell script during boot on Junos

I had recently to work on a situation where specific Junos configuration had to be applied on a device after reboot as a workaround. There are multiple solutions to this problem and the simplest one is to create a shell script that crontab will run after reboot. However, you need to make sure that you… Keep reading »

GRE tunnel between Juniper and Linux

This is a short howto about how you can bring up a GRE tunnel between Juniper devices and Linux, Ubuntu in this case. Just to provide some basics about GRE tunnels: Each endpoint has to have reachability to the other endpoint One endpoint must use the GRE tunnel to reach the destination of the tunnel(recursive… Keep reading »

Subnet-Router Anycast address on Junos

In this post we are going to discuss Subnet-Router Anycast address and how it is configured on Junos. The Subnet-Router anycast address is covered here: https://tools.ietf.org/html/rfc4291#section-2.6.1 The anycast address is the same as the unicast address from the interface with the difference that the interface identifier is set to zero. Any router on the subnet… Keep reading »

Getting MAC addresses using SNMP on EX2300/EX3400

In this post we are going to see how you can extract the content of the MAC address table using SNMP on EX2300 or EX3400. This is different than some other switching platforms like EX4200, EX4500, EX8200. To accomplish this, different Juniper enterprise MIBs must be used. Let us see how we can achieve this…. Keep reading »

Snapshots on EX2300/EX3400

In this post I will discuss about snapshots on EX2300 and EX3400. While the new FreeBSD version used in Junos releases after 15.1 is not specific to EX2300/EX3400, I will discuss more about them because I had access to these devices when I captured the outputs. However everything is applicable to the other platforms like… Keep reading »

Excluding interfaces from IRB State Calculations

As you know, in order you have an IRB up, you need to have at least one interface up on the VLAN for which the IRB is created. This condition is sometimes forgot by engineers troubleshooting why an IRB or RVI or SVI(in Cisco terms) is down. By default all interfaces part of the VLAN… Keep reading »

Proxy ARP on Junos

In this post I will discuss about Proxy ARP feature on Junos, more exactly on EX4200 platform. When a host sends an ARP Request to a switch configured with Proxy ARP, the switch send its own MAC address to resolve the ARP for the destination host and the source host starts to used the switch… Keep reading »