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--- zvm-notes [2020/12/19 20:03] – correcting stupid mistake prppedro
+++ zvm-notes [2021/01/04 10:48] (current) – [Some commands] prppedro
@@ Line 123: / Line 123: @@
 ===== Layer 2 shenanigans =====
-**WIP**
+Network [[https://en.wikipedia.org/wiki/OSI_model|Layer 2]] (Data Link) is, for a lot of reasons, the only layer whose adapters you can bridge. Bridging VM's is useful, sometimes. So you might want to bridge your z/VM system.
+Hercules presents two possible ways of letting your little private mainframe “talk” layer two. One of them is the newer and bleeding-edgy [[https://sdl-hercules-390.github.io/html/hercconf.html#QETH|QETH]]. The other one is the good and old LAN Channel Station emulation through IBM 3172, the [[https://sdl-hercules-390.github.io/html/hercconf.html#LCS|LCS driver]].
+==== QETH/QDIO ====
+QETH driver in Hercules has a neat feature: it lets you name your TUN/TAP devices. I named mine mainfrX. But you can use whatever you want. You can also call them manually tapX/tunX and be profoundly confused when they bridge/don't bridge. But I digress...
+QETH emulates OSA Express, which is just a very expensive mainframe-grade network card, from what I gather.
+On the guest side, it can be attached to a Virtual Switch. And that's really what the name says: it's an emulated network switch. Once your QETH adapter attaches to it, it act's as uplink port of sorts... **There's, however a catch**.
+=== The problem ===
+Maybe I'm a little dumb, but I wasn't able to get it working with z/VM's TCP/IP stack. It works with the default Layer 3 VSwitch. But attaching a QETH interface to such switch causes Hercules to open a TUN interface instead of a TAP one. So, yeah, no bridging. I ended up accepting that and using an internal network (10.5.5.0/24) just betwixt the host and z/VM. Also, I supposed attaching the QETH directly to the TCP/IP stack without a VSW will, most probably, open a TUN interface too.
+**Don't dismiss QETH's too quickly, though.** My [[zvm-linux|Linux]] guest uses virtual NIC's connected to VSW2 (a layer two switch I've configured manually) which is, in turn, connected with one of the QETH interfaces. Of course, for guests to be able to benefit from that, they need to support QDIO Ethernet (thus, Linux and latter versions of VM/ESA or OS/390, and beyond).
+==== LCS ====
+LCS is pretty easy to deal with. In fact, that's how I did with [[zvm-vmesa|VM/ESA]], in which it uses Hercules' LCS adapter passed through. Refer to the ''PROFILE TCPIP'', while I don't elaborate.
+UNIX/Linux creates a tapX interface which you can bridge.
 ===== Nice to know stuff =====
@@ Line 141: / Line 163: @@
      * **accessed**: lists the volumes/minidisks you're currently accessing;
   * **define** let's you, well, define things, like VSwitches[3].
+Also, ''[4]'' is a very good cheatsheet.
+==== Relevant files ====
+  * cf1 (cf0, depending on the sysgen):
+    * system config;
+    * Logo config files and logos, per se;
+  * each users own minidisk (generally at A)
+    * profile exec (things which executes automatically)
+  * tcpmaint's 198:
+    * profile tcpip
+    * system dtcparms (where you can bind stuff to TCPIP)
 ===== References =====
@@ Line 147: / Line 182: @@
   - [[https://www.ibm.com/support/knowledgecenter/en/SSB27U_6.4.0/com.ibm.zvm.v640.hcpl0/cksyssyn.htm|Steps for checking the syntax of the SYSTEM CONFIG file]]
   - [[https://www.vm.ibm.com/virtualnetwork/V23.pdf|z/VM Virtual Switches Basics]]
+  - {{ :quickref.pdf |}}

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