VPN 해제 후 공인 IP 기반 서비스 오픈과 보안 구성

기존에 VPN을 통해서만 접근 가능하던 웹 서비스를 VPN 해제 후 외부 공인 IP로 오픈해야 하는 일이 있었다.공인 IP를 받고... NAT 걸고... DMZ 설정과 프라이빗 존 설정까지 했는데도 접속이 안 됐고,원인은 허무하게도 DNS 였다ㅋㅋㅋ 정말 당연한 건데 그때는 왜 놓쳤을까?...지금 생각해 보면 너무 무식한 삽질이고 1년도 전에 있었던 일이지만..늦게나마 네트워크 관련 개념 복습할 겸 삽질한 기록을 남겨 본다. 1. 문제 상황기존에는 VPN 접속 환경에서만 접속 가능하도록 사설 IP 기반으로 DNS가 설정되어 있었다.이제 VPN을 걷어 내고, 서비스를 외부에 오픈해야 하는 상황이 되었다.1) VPN 제거2) 공인 IP 발급 및 할당3) NAT 설정4) DMZ 구간 및 내부 프라이빗 존 구..

https://www.hackerrank.com/challenges/append-and-delete/problem?isFullScreen=true Append and Delete | HackerRankCan you convert $s$ to $t$ by performing exactly $k$ operations?www.hackerrank.comYou have two strings of lowercase English letters. You can perform two types of operations on the first string:Append a lowercase English letter to the end of the string.Delete the last character of the s..

https://leetcode.com/problems/number-of-1-bits/description/Given a positive integer n, write a function that returns the number of set bits in its binary representation (also known as the Hamming weight). Example 1:Input: n = 11Output: 3Explanation:The input binary string 1011 has a total of three set bits.Example 2:Input: n = 128Output: 1Explanation:The input binary string 10000000 has a total ..

https://leetcode.com/problems/valid-palindrome/description/ A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.Given a string s, return true if it is a palindrome, or false otherwise. Example 1:Input: s = "A man, a plan,..

https://leetcode.com/problems/3sum/description/ Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.Notice that the solution set must not contain duplicate triplets. Example 1:Input: nums = [-1,0,1,2,-1,-4]Output: [[-1,-1,2],[-1,0,1]]Explanation: nums[0] + nums[1] + nums[2] = (-1) + 0 + 1 = 0...

https://leetcode.com/problems/climbing-stairs/You are climbing a staircase. It takes n steps to reach the top.Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top? Example 1:Input: n = 2Output: 2Explanation: There are two ways to climb to the top.1. 1 step + 1 step2. 2 steps Example 2:Input: n = 3Output: 3Explanation: There are three ways to climb to th..

https://leetcode.com/problems/valid-anagram/description/ Given two strings s and t, return true if t is an anagram of s, and false otherwise. Example 1:Input: s = "anagram", t = "nagaram"Output: trueExample 2:Input: s = "rat", t = "car"Output: false Constraints:1 s and t consist of lowercase English letters.The problem was to check whether two given strings contain the same kinds of characters i..

https://leetcode.com/problems/longest-consecutive-sequence/description/Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.You must write an algorithm that runs in O(n) time. Example 1:Input: nums = [100,4,200,1,3,2]Output: 4Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.Example 2:Input: nums ..

https://leetcode.com/problems/top-k-frequent-elements/description/Given an integer array nums and an integer k, return the k most frequent elements.You may return the answer in any order. Example 1:Input: nums = [1,1,1,2,2,3], k = 2Output: [1,2] Example 2:Input: nums = [1], k = 1Output: [1] Example 3:Input: nums = [1,2,1,2,1,2,3,1,3,2], k = 2Output: [1,2] Constraints:1 -10^4 k is in the range [1..

https://leetcode.com/problems/contains-duplicate/description/ Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct. Example 1:Input: nums = [1,2,3,1]Output: trueExplanation:The element 1 occurs at the indices 0 and 3. Example 2:Input: nums = [1,2,3,4]Output: falseExplanation:All elements are distinct. Example 3:I..