https://createnetech.tistory.com/ Network Engineer In South Korea. Cloud & Data Center Network. ko Mon, 13 Apr 2026 14:22:16 +0900 TISTORY 100 ejunwiths https://createnetech.tistory.com/62   When I send DNS request, I will get some response. At this time, I had some question if this answer come from cached information or not. Someone think like me.   When the DNS server can recurse (RA is set) 1. Even if the query is recursive or .. System Basic Engineering/OpenSource ejunwiths https://createnetech.tistory.com/62 https://createnetech.tistory.com/62#entry62comment Wed, 23 Sep 2020 21:56:32 +0900 https://createnetech.tistory.com/61 Sometimes, I need to use "dig trace" command. I have known that it trace the DNS hop by hop. In this post, I will see the Packet level with this command.   1. First Packet of dig trace.   The first packet is look like.  There are 3 propert.. System Basic Engineering/OpenSource ejunwiths https://createnetech.tistory.com/61 https://createnetech.tistory.com/61#entry61comment Wed, 23 Sep 2020 15:05:49 +0900 https://createnetech.tistory.com/60 In the past, I posted "how to configure bind9". During writing, I did not understand fully the concept of the recursion, even if there are simple explain like others. I will see the some packet in this post. It is much easier.   1. General DNS Stand.. System Basic Engineering/OpenSource ejunwiths https://createnetech.tistory.com/60 https://createnetech.tistory.com/60#entry60comment Wed, 23 Sep 2020 13:27:13 +0900 https://createnetech.tistory.com/58 Window size value : This is the value to receive from other side. (Window size is advertising the RCV buffer space available for the device, how much memory is allocated for the session)   The maximum field for TCP window size = 65535 or 0xFFFF .. Network Engineering/Basic Learning ejunwiths https://createnetech.tistory.com/58 https://createnetech.tistory.com/58#entry58comment Wed, 2 Sep 2020 17:27:13 +0900 https://createnetech.tistory.com/57 Sometimes, I need to see the packet with wireshark tool. I have to calculate sequence numbers. I have learned the IP packet size is 1540 (MSS is 1460). However, I can see the more size in the packet. This post is good for me.     This is whole .. Network Engineering/Basic Learning ejunwiths https://createnetech.tistory.com/57 https://createnetech.tistory.com/57#entry57comment Wed, 2 Sep 2020 16:57:17 +0900 https://createnetech.tistory.com/56 1. Simple OSPF Parameters to Use Before configuring the OSPF, I will handle some concept necessary to configure. For interface configuration, there is some term of network type. In this blog, those are compared simply. In the above, DR/BDR terms are.. Network Engineering/Basic Learning ejunwiths https://createnetech.tistory.com/56 https://createnetech.tistory.com/56#entry56comment Fri, 5 Jun 2020 21:09:05 +0900 https://createnetech.tistory.com/55 Recently, I have some chance to study about the FRRouting. At that time, I do not have any Linux server. Thus, I decide that I use AWS Spot instance. After installation, I set up the OSPFv2 environment with simple configuration. However I can not estabili.. Cloud Study/AWS ejunwiths https://createnetech.tistory.com/55 https://createnetech.tistory.com/55#entry55comment Fri, 5 Jun 2020 00:59:32 +0900 https://createnetech.tistory.com/54 A few years ago, I have read about Quagga. It is software router which can install on the Linux such as Ubuntu. I have heard about this FRRouting which is next generation of the Quagga. In this post, I will configure some feature from FRRouting.   1... Network Engineering/OpenSource ejunwiths https://createnetech.tistory.com/54 https://createnetech.tistory.com/54#entry54comment Wed, 3 Jun 2020 22:20:05 +0900 https://createnetech.tistory.com/53 In this post, I handled the External BGP routing. In this part, I will address Internal BGP routing which is working on the same AS number. This is the my environment Top of the hosts will be the router as reflector. And the others are reflector-client. .. Network Engineering/OpenSource ejunwiths https://createnetech.tistory.com/53 https://createnetech.tistory.com/53#entry53comment Mon, 11 May 2020 00:25:33 +0900 https://createnetech.tistory.com/52 Recently, I need to study about Calico over Kubernetis. In fact, I like Flannel rather than this. However, this Calico is also best practice. During start this Calico, I read about the Brid. In this post, I will how to install and configure this Bird. &nb.. Network Engineering/OpenSource ejunwiths https://createnetech.tistory.com/52 https://createnetech.tistory.com/52#entry52comment Sun, 10 May 2020 15:58:59 +0900