Author: rtoodtoo

Genco has worked for more than 10 years as a Network/Support Engineer. He is also interested in Python, Linux, Security and SD-WAN, currently lives in the Netherlands and works as a Network Support Engineer at Tesla Inc. // JNCIE-SEC #223 / RHCE / PCNSE

Slow file transfer and TCP Zero Window Probe

Slow file transfers must be really bothering everyone. I have a ZyXEL NSA325 NAS device which has a gigabit interface but I am getting extremely low throughput. Unfortunately this has been a problem I think since I bought this device. Now I could finally get hold of time to troubleshoot the issue. Here is my
Read More »

OSPF route withdraw

OSPF has slightly different way of removing routes compared to BGP. On this short post, I will present how a link failure is propagated to other routers on OSPF domain. For this test, I have the following topology section in which AREA3 is connected to AREA0 and we simulate a link failure on the Junos
Read More »

BGP Route Refresh in JUNOS

What happens when you change a BGP import routing policy in your neighbor configuration? Changes take effect immediately or we need to issue the soft-inbound command to request the routes? Let’s see by an example. We received the route 10.83.0.0/24 from 10.82.1.9 already as you see below. root@J29> show route protocol bgp terse 10.83.0.0/24 inet.0:
Read More »

BGP open message receives a TCP RST

On this micro post, I would like to show one reason why a BGP open message receives a TCP RST. For this test, I set up a BGP neighborship between two peers: PeerA(10.82.1.9) and PeerB(10.82.1.10) PeerA initiates the connection and look what happens in the packet capture. According to the sequence, TCP seems to have
Read More »

OSPF Loop prevention

On this post, I will show an example of loop prevention on OSPF protocol. There is a nice document at here about the principles of loop prevention. What I will just do is to show this on Junos. In order to show this, I am using the following topology; On this topology, J40 and J32
Read More »

OSPF equal cost path

On this post, I will try to show how OSPF behaves when there are two equal cost paths towards a destination. To demonstrate this, I have prepared my usual topology. On this topology all routers are running OSPF but our focus is on the router J32 which is circled at the bottom and our destination
Read More »

SRX Tips: Default application timeouts

It can be annoying if you are new to SRX and your SSH connection towards the firewall keeps timing out. You can of course activate keep alive on your SSH client or play with the default ssh timeout on SRX itself. First let’s see how we can check the current timeout. root@J200> start shell user
Read More »