Pretty good though the English could be slightly clearer in the first few paragraphs:
- Here, PC A wants to send traffic to PC B at IP address 192.168.1.6. - I'd insert 'at IP address 192.168.1.5' after 'PC A'. I'm also not sure if 'Here, ' adds anything.
- Within a layer 2 switch environment exists a broadcast domain. - a comma and the word 'there' should be inserted after 'environment'
It might also be worth mentioning that L3 routing can be done by an MX at the end of the article?